Everything the product produces is a doc, and every doc keeps its history.
Versions
Changing a doc adds a version rather than overwriting it. The latest version is what you see; earlier ones stay readable.
This matters because most changes here are made by machine. A run that rewrites a document you had reviewed cannot destroy your copy — it adds to the record, and you can see what changed.
Reading an older version
The version selector in the doc header opens earlier versions.
Docs and interfaces
A doc may carry an interface — a sheet, a board, a deck — or it may be plain prose. The interface is part of the doc and versions with it, so an older version shows the sheet as it was.
Where docs live
Inside a directory, organised into categories, tabs and sections. That structure is what the sidebar renders and what Memory tabulates.
Deleting
Deleting removes a doc and its versions. Prefer archiving for anything you may want back.