What does "Keep this updated" do?

It files the later documents of that kind by themselves, so your room stays current without anyone opening the Inbox. Tick it on a document in the Inbox, or on the document's page once it's filed:

• For most kinds, each new one becomes a new version of the same document: its link and reading report carry on, and investors see the latest version, marked Updated.
• For monthly accounts and bank statements, each new month is a new document in the same folder as the month before.
• HR policies are kept updated one policy at a time, and bank statements one bank account at a time.

Your team gets a note for each one filed; investors get no email unless you tell them. A file of another type, such as a policy that was a PDF and is now a Word file, still waits in the Inbox. The same file sent again is left out.

To stop, untick it on the document's page, or an Owner chooses Stop in Company settings (click your picture at the top right, then Company settings), under Connections, which lists what's kept updated and who ticked it. New ones then wait in the Inbox again.