Glossary
Biome
Biome is Apple's newer event framework that stores macOS activity streams such as App.InFocus in SEGB files, taking over many knowledgeC.db streams.
Biome is Apple's newer framework for recording context and "pattern of life" events. It has taken over many streams that used to live in knowledgeC.db, including application focus. Instead of one SQLite database, each stream is a folder of binary SEGB files whose records usually carry a protobuf payload.
User streams sit under ~/Library/Biome/streams/restricted/<Stream>/local/ and ~/Library/Biome/streams/public/<Stream>/local/. Records synced from other devices on the same Apple Account arrive in <Stream>/remote/<device UUID>/, and expired files move to local/tombstone/. System streams live in /private/var/db/biome/streams/, owned by _biome.
The layout matters to an investigator: remote records must not be attributed to the Mac under examination, and tombstone files are often skipped by parsers. For how Biome relates to the older store, read knowledgeC vs Biome.