# Clusters

> Index passages from your books, notes and Bases, find the topics they share and answer questions with cited cards.

Clusters reads a set of documents passage by passage and writes a **card** for what each passage says: a concept, a claim, a case, a practice. Every card quotes its passage, so you can always open the text behind it.

With the cards made, you can search them by meaning, find the topics a collection keeps returning to, see where two books disagree, and draft a write-up whose every quote is checked against its source. Topics are written as notes, so Obsidian's Graph view shows the clusters.

## The words to know

| Word | What it is |
|---|---|
| **Collection** | A set of documents Clusters reads: books on a shelf, notes in a folder or with a tag, or the rows of a Base. One note describes each collection. |
| **Lens** | What is pulled out of each passage and what gets compared. Two are built in: **nonfiction** and **fiction**. You can make your own. |
| **Passage** | A piece of a document: a chapter section, a story, a note, or one heading of a long note. |
| **Card** | What the lens found in a passage, with a quote (its **anchor**) from the text. |
| **Topic** | A group of cards that say similar things, with a name and a note of its own. |
| **Run** | One job that wrote something: indexing, a survey, finding topics, a draft. Each can be undone. |

## What you need

- Obsidian 1.11.4 or later, on desktop.
- **Model Hub**, required. It holds your model providers and keys, and records what each call costs. Clusters never holds a key.
- **Books & Shelves**, only for collections of books. It reads your Calibre library. Notes and Bases work without it.

Next: [Getting started](getting-started.md).