ATProto

Record: Stores actions like posts and follows as JSON objects. Each user can only modify their own Records.
Blob: Binary files such as images and videos.
Lexicon: Defines Record structure (schema). Bluesky-specific ones use app.bsky.*, common ones use com.atproto.*.
DID: Unique account identifier. Permanent, while handles can change freely.
Handle: Domain format (@user.com). Mapped to DID, so relationships are maintained even when changed.
AT URI: Uniquely refers to Records in the format at://<DID>/<lexicon>/<rkey>.
Repo: Personal storage containing all user data (Records, Blobs).

PDS (Personal Data Server): Stores each user's original data. Migration between PDSs is possible.
Relay: Combines event streams (firehose) from multiple PDSs to provide a complete network stream.
Jetstream: Lightweight JSON version of Relay output.
AppView: API server used by clients. Provides processed data like follower counts, likes, search, timelines. (Bluesky uses a large-scale ScyllaDB version)
CDN: Optimizes image and video delivery.

Labeller: Third-party moderation service. Can apply labels to block or warn about content/users.
Feed Generator: Service that provides custom feeds created by anyone. (Keywords, algorithm-based recommendations, etc.)
Client App: Web/mobile clients like bsky.app. Loads data through PDS and AppView.
DM: Currently a temporary centralized service (chat.bsky.*), with plans to apply E2E encryption standards long-term.