Backup, Archive, Data, - where are they stored and how to recover them

Frequently Asked Questions
1
  • I see there are buttons/clickable text/folders with these titles and that there is an archive folder in local folders, and that clicking ‘archive’ button with a message highlighted moves the message to that folder
  • but there are no ‘data’ in 'data files > files

So please may I ask

  1. what is ‘backup’ and where does it go?
  2. how may ‘archive’ be recovered?
  3. what does ‘data’ signify?
  4. are they all included in export/import?