In Apple Mail in MacOS High Sierra I move all old sent and received mails out of the IMAP folders into a folder that is displayed as "Local" in the sidebar:
That way I archive all my old mails and remove them from the IMAP folders from the internet. Whenever I get a new Mac, I export those local folders and import them back into Mail on the new Mac. So my archive stays complete and searchable.
But Apple also has this thing called "Archive":
Which is not displayed under "Local" but its content is actually stored under local.
So what is the actual functional difference between the two, except from them having different icons?
Best Answer
The 'Archive' folder that Apple Mail uses with IMAP accounts is still on the IMAP server.
In short, it's just a default folder to move email to, for people who like their Inbox empty.