Backups
Creating, restoring, downloading. And how many you get to keep.
Creating one
A backup packs your whole server directory. How many you may keep at once is your plan's business; when the slots are full, delete an old one first.
The cleanest backup is one taken with the server stopped. On a running server the world may be mid-write, and that can show up when you restore.
Restoring
Restoring replaces the current state completely. Anything that happened since the backup is gone afterwards. The interface asks once, and that is the only confirmation you get.
Where they live
Backups sit on the same node your server runs on. This is not off-site storage in a different data centre.