I don't get what this project does

[Fazel94]

I know and use borg and btrfs in production.
After reading README.md and some of the code I still don't get why this is useful.
Does it backup btrfs to borg? or borg to btrfs?

[sten0]

Btrfs to borg. I'm guessing you were looking at the devel branch instead of the master one? Please use tagged released, they're tested and reliable, and the nascent python rewrite has stalled. ie. the devel branch is non-functional