OpenStreetMap

1. Elements: Nodes, Ways and Relations

   The OSM data primitives: nodes, ways, relations, and how geometry is represented.

2. Tags and Map Features

   Key=value tagging, tagging conventions, and the standard Map Features taxonomy.

3. OSM Editing API v0.6

   Reading and writing map data through changesets, element CRUD, and map bounding box calls.

4. Changesets

   Grouping edits into changesets, discussions, tags, and versioning of elements.

5. OAuth Authentication

   Registering applications and authorizing users with OAuth 2.0 for API access.

6. OSM File Formats

   OSM XML, PBF, and change formats used to exchange map data.

7. Planet.osm and Extracts

   Downloading the full planet file, regional extracts, and replication diffs.

8. Overpass API

   Read-only querying of OSM data with the Overpass API server.

9. Overpass Query Language

   Writing Overpass QL queries with filters, bounding boxes, recursion, and output modes.

10. Nominatim Geocoding

    Geocoding and reverse geocoding OSM data with Nominatim search and lookup APIs.

11. Slippy Map Tiles

    Zoom levels, x/y tile numbering, and converting coordinates to tiles.

12. Tile and Nominatim Usage Policies

    Acceptable use limits, attribution, and caching rules for OSM-hosted services.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.