git is a version control system, a little like SVN. However, it differs in an important way, that it is a distributed system, where every working copy stores the full version history. This means that changes, branches and so on can be performed locally and then synchronized with other working copies. It is much faster than SVN.
git by default allows connection to remote servers through ssh. However, if a server is protected by a key file, rather than a password, I didn't know how to specify this it git. I found the answer today here - to modify the "~/.ssh/config" file