rm stands for remove
r tells to delete everything in the directory
f tells to ignore warning messages during deletion
https://developers.slashdot.org/story/16/04/14/1542246/man-deletes-his-entire-company-with-one-line-of-bad-code
http://serverfault.com/questions/769357/recovering-from-a-rm-rf
A comment on backups is as follows:
Backups need to be offsite, offline, and incremental. That you could delete them from your main server means they weren't what I would call backups. – Tim