I too am not entirely sure what GIT is, though I have a general idea.
However, although I don't normally like mentioning software from other sources on a forum like this, I think it might well be worth your taking a look at Scrivener (
www.literatureandlatte.com). I don't know about using it with a GIT repo, it does interface to a certain extent with Subversion, though I can't think of anyone who is using it like that.
It does have it's own "Backup to" command built in, and a "snapshot" feature which allows the user to take a snapshot of their work in progress at any point to keep that as a version they can go back to. I haven't had to use "snapshot" myself, so have no personal experience of it.
Mark
Disclaimer: I am not in any way connected with Literature & Latte, just a very happy user of Scrivener.