afaik we're not there yet so wait for the android release proper. git is a version control software for software developers, I write some come then I issue a command to my pc to create a snapshot of all my files. Then I write some more code and because I'm shit I fuck it up and write lots of bugs. I can then issue a command to revert my files back to that snapshot when there are no bugs. 

Github is a place for many developers to do that collaboratively. There's much more to Git and Github but that's more or less the high level version of what they do.

Git was created by Linus Torvalds, the same dude who wrote the og Linux kernel software.