What does my host actually back up?

I run <stack> on <host>. I'm assuming the host backs things up, and I
want to know whether that assumption is safe.

Find out and tell me:
- What exactly is backed up: files, databases, email, configuration?
- How often, how many copies are kept, and for how long?
- Are the backups stored somewhere other than the server they back up?
- How do I restore, and is restoring free or a paid support request?
- Can I restore one file or one table, or only everything at once?

Then list what isn't covered, and give me the smallest backup of my own
that covers the gap.