---
title: .md files and CLAUDE.md — Claude basics, lesson 5
description: A .md file is plain text with a few marks: a document for people, instructions for Claude. What CLAUDE.md is, and how a line with @ imports a whole file.
url: https://instibrain.ai/guides/claude-basics/md-files-and-claude-md
updated: 2026-10-28
site: https://instibrain.ai/llms.txt
---

lesson 5 of 7 · claude basics

# .md files and CLAUDE.md.

A .md file is plain text with a few marks for headings and lists. People read it as a document; Claude reads it as instructions.

## new words

**Markdown**
The name of those marks. A Markdown file ends in `.md`.

**Import**
A line with `@` and a file's path. It pulls that whole file in.

## the lesson

| You type | It becomes |
| `# Website pages` | a heading |
| `- Title under 60 characters` | a list item |
| `**60 characters**` | bold text |
| `[the brand rules](brand.md)` | a link to another page |
| `@rules/writing.md` | the whole of that file, pulled in |

`CLAUDE.md` is a Markdown file with that exact name. Claude reads it at the start of every session. Good instructions are short and exact. "Titles stay under 60 characters" works; "write good titles" does not.

Claude follows a `CLAUDE.md`, but the file cannot force Claude. A hard stop comes from permissions, the next lesson.

In instibrain, every page is a .md file, and the setup turns Claude's own memory off. So a lesson you learn goes onto a page, where the people you work with find it. instibrain basics shows which page.

# makes a heading, - a list item, ** bold, [text](file) a link. A line with @ and a path imports that file.

## try it

Type this and press Enter:

```
Show me ~/instibrain/CLAUDE.md, line by line.
```

## you should see

- Lines that start with `@`. Each one imports another .md file: the first is instibrain itself, the next your own Personal layer.
- Any other line is a note about this computer.

---

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