It allows you to observe and interact with the history of refs like HEAD, so superficially destructive operations like amending a commit can be recovered, rever

It allows you to observe and interact with the history of refs like HEAD, so superficially destructive operations like amending a commit can be recovered, reverted, etc. It's kind of like meta-git, allowing version control operations on the version control system. It's a lifesaver when you botch a merge or something and allows you to do "destructive" operations fearlessly (up to a point, you can munge a git repo pretty bad if you try hard enough).