# Learnfold

> Learnfold is an iPhone and iPad app that turns a question, a link, or a PDF into a short course. You read it at your own pace, ask about any sentence, and follow a side question into a lesson of its own. It uses AI to write explanations, and AI can make mistakes.

The free courses below are written by the Learnfold team and ship inside the app. Every course has a web page, a page per lesson, and a Markdown copy with the full text. In the app, each course can also be personalized: the tutor asks what the learner already knows and builds their own version.

## Free courses

- [How LLMs actually work](https://learnfold.app/learn/llms/): What happens between pressing send and reading the reply. 9 lessons, 35–45 min. Full text: https://learnfold.app/learn/llms/course.md
- [How the internet actually works](https://learnfold.app/learn/internet/): Follow one web page from your screen to a server and back. 6 lessons, 20–30 min. Full text: https://learnfold.app/learn/internet/course.md
- [Why you remember and forget](https://learnfold.app/learn/memory/): How memories form and fade, and what that means for how you study. 6 lessons, 20–30 min. Full text: https://learnfold.app/learn/memory/course.md
- [Black holes, without the math](https://learnfold.app/learn/black-holes/): A place even light can't leave, and how we know it's really out there. 6 lessons, 20–30 min. Full text: https://learnfold.app/learn/black-holes/course.md
- [How money grows](https://learnfold.app/learn/money/): Why time beats talent, and what you're actually buying when you invest. 6 lessons, 20–30 min. Full text: https://learnfold.app/learn/money/course.md
- [How the Roman Republic fell](https://learnfold.app/learn/roman-republic/): A century of broken rules, from the Gracchi to Augustus. 6 lessons, 20–30 min. Full text: https://learnfold.app/learn/roman-republic/course.md

## Wait, how?

- [Why does spilled coffee leave a ring?](https://learnfold.app/wait-how/coffee-ring-effect/): A drying coffee drop's edge sticks in place, so liquid flows outward to replace what evaporates and carries the coffee along. How scientists stop it. Markdown: https://learnfold.app/wait-how/coffee-ring-effect/index.md
- [How does a chatbot pick the next word?](https://learnfold.app/wait-how/how-a-chatbot-picks-the-next-word/): A chatbot writes one piece at a time. The model gives every possible next piece odds, and a few lines of code roll loaded dice to pick one. Markdown: https://learnfold.app/wait-how/how-a-chatbot-picks-the-next-word/index.md
- [What causes brain freeze?](https://learnfold.app/wait-how/how-brain-freeze-works/): Cold on the roof of the mouth or the back of the throat sets off nerves and fast blood flow changes in the head. What studies show, and what is still argued. Markdown: https://learnfold.app/wait-how/how-brain-freeze-works/index.md
- [Where does a photo actually go when you back it up to the cloud?](https://learnfold.app/wait-how/how-cloud-photo-storage-works/): Your photo is encrypted, uploaded, split into pieces and stored on many disks in several buildings. What happens step by step, and what varies by provider. Markdown: https://learnfold.app/wait-how/how-cloud-photo-storage-works/index.md
- [How does GPS know where you are?](https://learnfold.app/wait-how/how-gps-works/): GPS satellites broadcast only time and position. Your phone listens to four or more, turns signal delays into distances and solves for where it is. Markdown: https://learnfold.app/wait-how/how-gps-works/index.md
- [How does an induction stove heat a pan?](https://learnfold.app/wait-how/how-induction-cooktops-work/): An induction stove doesn't heat the glass. A coil under it makes a flipping magnetic field that drives currents in a steel or iron pan, and the pan heats itself. Markdown: https://learnfold.app/wait-how/how-induction-cooktops-work/index.md
- [How do noise-cancelling headphones work?](https://learnfold.app/wait-how/how-noise-cancelling-headphones-work/): Microphones hear the noise, the headphones play it back inverted, and the two cancel. Why it beats engine drone but not voices, and what the ear cushions do. Markdown: https://learnfold.app/wait-how/how-noise-cancelling-headphones-work/index.md
- [How do planes stay up?](https://learnfold.app/wait-how/how-planes-stay-up/): Wings turn air downward, and that creates lower pressure above and higher pressure below. Why equal transit time is wrong, and what a stall really is. Markdown: https://learnfold.app/wait-how/how-planes-stay-up/index.md
- [How do QR codes work?](https://learnfold.app/wait-how/how-qr-codes-work/): Three corner squares help a camera find a QR code, and it still scans with part of it damaged. At level H, error correction recovers about 30% of the data. Markdown: https://learnfold.app/wait-how/how-qr-codes-work/index.md
- [How did someone fit a computer inside a language model?](https://learnfold.app/wait-how/how-qwenputer-works/): Qwenputer compiles a RISC-V CPU into the weights of Qwen3.5-4B and uses the model's own memory state as RAM. How it works, and what it can't do yet. Markdown: https://learnfold.app/wait-how/how-qwenputer-works/index.md
- [How does an SSD remember things with the power off?](https://learnfold.app/wait-how/how-ssds-keep-data-without-power/): An SSD traps electrons behind a thin insulating wall in each flash cell. With no voltage to push them, they stay, for years but not forever. Markdown: https://learnfold.app/wait-how/how-ssds-keep-data-without-power/index.md
- [How do tides work?](https://learnfold.app/wait-how/how-tides-work/): The Moon pulls harder on the near side of Earth than the far side, stretching the oceans into two bulges. Why the Sun counts for half and Fundy goes wild. Markdown: https://learnfold.app/wait-how/how-tides-work/index.md
- [How does Wi-Fi carry data on radio waves?](https://learnfold.app/wait-how/how-wi-fi-works/): Wi-Fi is an ordinary radio wave. It carries bits by bending the wave's timing and height, in dozens of thin lanes at once, from several antennas. Markdown: https://learnfold.app/wait-how/how-wi-fi-works/index.md
- [How does your phone know which way is up?](https://learnfold.app/wait-how/how-your-phone-knows-which-way-is-up/): Inside your phone is a tiny weight on springs. It feels the pull of gravity, reads zero in free fall, and needs a gyroscope to tell a tilt from a shove. Markdown: https://learnfold.app/wait-how/how-your-phone-knows-which-way-is-up/index.md
- [Why does the same note sound different on a piano and a guitar?](https://learnfold.app/wait-how/same-note-different-sound/): Same pitch, different sound. How harmonics, the way a string is set moving and how a note fades over time give each instrument its timbre. Markdown: https://learnfold.app/wait-how/same-note-different-sound/index.md
- [What do bees see that you can't?](https://learnfold.app/wait-how/what-bees-see/): Bees see ultraviolet light, so many flowers carry patterns invisible to us. How bee colour vision works, what happens with red, and what is still a guess. Markdown: https://learnfold.app/wait-how/what-bees-see/index.md
- [Why did the blue LED take thirty years?](https://learnfold.app/wait-how/why-blue-leds-were-so-hard/): An LED makes light when electrons drop across a gap in a crystal. Blue needs a wide gap, and the material for it took three decades to tame. Markdown: https://learnfold.app/wait-how/why-blue-leds-were-so-hard/index.md
- [Why does bread rise?](https://learnfold.app/wait-how/why-bread-rises/): Yeast turns sugar into carbon dioxide, gluten holds the gas in, and the oven adds a last burst. What really happens, plus what sourdough changes. Markdown: https://learnfold.app/wait-how/why-bread-rises/index.md
- [Why do stars twinkle but planets mostly don't?](https://learnfold.app/wait-how/why-stars-twinkle/): Stars look like points, so moving pockets of air make their light flicker. Planets show tiny discs that average it out. The physics, plus the exceptions. Markdown: https://learnfold.app/wait-how/why-stars-twinkle/index.md

## Guides

- [How to turn a reading list into a learning plan](https://learnfold.app/guides/build-a-reading-list-into-a-plan/): A reading list is a pile, not a plan. Set a goal, triage every item, order by prerequisites, time box each pass and schedule returns. Markdown: https://learnfold.app/guides/build-a-reading-list-into-a-plan/index.md
- [How to check an AI explanation for mistakes](https://learnfold.app/guides/check-ai-explanations-for-mistakes/): A practical checklist for catching errors in AI explanations. Pull out the claims, check sources, test with examples and watch for confident vagueness. Markdown: https://learnfold.app/guides/check-ai-explanations-for-mistakes/index.md
- [How to learn from an article or web page without just skimming it](https://learnfold.app/guides/learn-from-a-link/): Skimming a good article feels like learning and mostly is not. A six-step way to study a web page with an AI tutor and check it against the source. Markdown: https://learnfold.app/guides/learn-from-a-link/index.md
- [How to study a textbook chapter with an AI tutor](https://learnfold.app/guides/study-a-textbook-chapter-with-ai/): Use an AI tutor for the study habits with the best evidence, practice testing and spacing, instead of letting it summarize the chapter for you. Markdown: https://learnfold.app/guides/study-a-textbook-chapter-with-ai/index.md
- [How to turn a PDF into a course](https://learnfold.app/guides/turn-a-pdf-into-a-course/): A plan-first way to turn a PDF into a course you can study. Check the file, approve the outline, read in sections and verify what matters. Markdown: https://learnfold.app/guides/turn-a-pdf-into-a-course/index.md
- [How to ask an AI tutor better questions](https://learnfold.app/guides/write-better-questions-for-an-ai-tutor/): Vague questions get textbook answers. Six ways to ask an AI tutor better questions, with before and after examples you can copy and adapt. Markdown: https://learnfold.app/guides/write-better-questions-for-an-ai-tutor/index.md

## Use cases

- [An AI course generator for iPhone that shows you the plan first](https://learnfold.app/use-cases/ai-course-generator-iphone/): Learnfold turns a question, link, PDF or photo into a course on your iPhone. You approve the plan first, then lessons are written section by section. Markdown: https://learnfold.app/use-cases/ai-course-generator-iphone/index.md
- [An AI tutor you can interrupt mid-lesson](https://learnfold.app/use-cases/ai-tutor-you-can-question/): Select a sentence in a lesson and ask why. Learnfold saves the discussion so you can reopen it, and wrong answers on a check can turn into a conversation. Markdown: https://learnfold.app/use-cases/ai-tutor-you-can-question/index.md
- [Follow a rabbit hole without losing the thread](https://learnfold.app/use-cases/follow-your-curiosity-rabbit-hole/): Every Learnfold lesson ends with a choice to go deeper, sideways or zoom out. A course map with a You are here marker shows where your questions took you. Markdown: https://learnfold.app/use-cases/follow-your-curiosity-rabbit-hole/index.md
- [How to learn a topic from scratch with Learnfold](https://learnfold.app/use-cases/learn-anything-from-scratch/): Starting from zero? Here are the first ten minutes in Learnfold, from typing a question and approving a plan to reading a page and checking yourself. Markdown: https://learnfold.app/use-cases/learn-anything-from-scratch/index.md
- [A self-paced learning path that you steer](https://learnfold.app/use-cases/self-paced-learning-path/): Approve a course plan, read at your own pace, and pick up on the exact page where you stopped. Learnfold courses and progress can sync through iCloud. Markdown: https://learnfold.app/use-cases/self-paced-learning-path/index.md
- [Turn your study notes into a course](https://learnfold.app/use-cases/study-notes-to-course/): Give Learnfold your lecture notes as text, Markdown, a PDF or a photo and it plans a course from them. Approve the plan, read short lessons, edit any page. Markdown: https://learnfold.app/use-cases/study-notes-to-course/index.md

## Compare

- [Learnfold vs other AI tutor and course apps on iPhone](https://learnfold.app/compare/learnfold-vs-ai-tutor-apps/): How Learnfold compares with Wondering, Socrati, StudyFetch, Mindgrasp and YouLearn, using each app's own App Store listing. Where each one is the better pick. Markdown: https://learnfold.app/compare/learnfold-vs-ai-tutor-apps/index.md
- [Learnfold vs ChatGPT for learning](https://learnfold.app/compare/learnfold-vs-chatgpt-for-learning/): ChatGPT study mode now has quizzes and flashcards. Learnfold turns a question, link or PDF into a course of linked pages. When each one is the right pick. Markdown: https://learnfold.app/compare/learnfold-vs-chatgpt-for-learning/index.md
- [Learnfold vs flashcard apps like Anki and Quizlet](https://learnfold.app/compare/learnfold-vs-flashcard-apps/): Anki and Quizlet help you remember. Learnfold helps you understand a topic first. When flashcards win, when a course wins, and how to use them together. Markdown: https://learnfold.app/compare/learnfold-vs-flashcard-apps/index.md
- [Learnfold vs NotebookLM, now called Gemini Notebook](https://learnfold.app/compare/learnfold-vs-notebooklm/): NotebookLM became Gemini Notebook in July 2026. How its source-grounded notebooks compare with a Learnfold course that grows from your questions. Markdown: https://learnfold.app/compare/learnfold-vs-notebooklm/index.md
- [Learnfold vs Coursera, edX, Udemy and Khan Academy](https://learnfold.app/compare/learnfold-vs-online-course-platforms/): Course platforms offer expert-made courses and certificates. Learnfold writes a personal course from your question. Who needs a certificate, and who does not. Markdown: https://learnfold.app/compare/learnfold-vs-online-course-platforms/index.md
- [Learnfold vs YouTube and Wikipedia for learning](https://learnfold.app/compare/learnfold-vs-youtube-and-wikipedia/): YouTube and Wikipedia are free and often enough. What an AI-written course adds, what it costs you in trust, and how to use the free resources alongside it. Markdown: https://learnfold.app/compare/learnfold-vs-youtube-and-wikipedia/index.md

## About Learnfold

- [Learnfold home](https://learnfold.app/): what the app does, pricing, and FAQ
- [Learnfold on the App Store](https://apps.apple.com/us/app/learnfold/id6794672797)
- [Privacy policy](https://learnfold.app/privacy)
- [Support](https://learnfold.app/support)

## Optional

- [Every course and article in one file](https://learnfold.app/llms-full.txt)