> ## Documentation Index
> Fetch the complete documentation index at: https://docs.asakiri.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Course structure

> Units, lessons, and parts: the outline learners move through.

A course is organized as **units**, **lessons**, and **parts**.

| Level | What it is | Holds |
| - | - | - |
| **Unit** | Groups lessons and forms the course outline | An ordered list of lesson IDs |
| **Lesson** | A heading learners move through | An ordered list of parts |
| **Part** | The unit of content | One rich-text document, rich-media composition, or exercise |

A lesson holds no content of its own. It is an ordered list of parts, and a single
lesson usually mixes them, for example a rich-text introduction followed by a few
exercises.

## Part kinds

Each part is exactly one of:

* **Rich-text document:** a [Tiptap](https://tiptap.dev) document for explanations and
  reading material.
* **Rich-media composition:** a layout of fragments that bind to content and assets.
* **Exercise:** one of the [exercise types](/data-structure/exercises).

<Note>
  The content kinds (rich-text, rich-media, exercise) classify a **part**, not a lesson.
</Note>

## Ordering

Ordering is meaningful at every level. Units list lessons in order, lessons list parts
in order, and collections list records in order. For a writing system, that record order
captures the canonical sequence (for example the gojūon order of kana). See
[Content records](/data-structure/content-records#writing-systems).


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