archive

baileymoon wrote:

What is the archive for and what is the criteria for what goes into it

And what app in particular is your query? Mail?

From the Mail>Help>Archive

Archive emails in Mail on Mac

You can store email messages in an Archive mailbox—for example, to quickly find them later when you’re ready to take action.

Open Mail for me

1. In the Mail app on your Mac, select one or more messages.
2. If you select a conversation, any message in the conversation that’s in the current mailbox—for example, the Inbox—will be archived; related messages that are in other mailboxes will not be archived.
3. Click the Archive button in the Mail toolbar (or use the Touch Bar).
4. If you set the “Move discarded messages” option to Archive in Viewing preferences in Mail, you can archive messages from Mail notifications. Just move the pointer over the Mail notification, then click Archive.

Mail creates an Archive mailbox in the Mail sidebar for each account whose messages you’re archiving, and moves the messages there. To view them, click the mailbox. Archived messages remain there until you delete or move them.