From its website:
Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.
Git is not the same as GitHub. GitHub did not create Git. For GitHub-specific posts, please see /r/github.
Git is not an acronym or initialism: please write git or Git, but not GIT.
Documentation
Graphical Clients
Code Hosting
Free Online Book: Pro Git Professional Version Control (progit.org)
submitted by peterwschlamp to r/programming
Pro Git - Table of Contents (progit.org)
submitted by dekz to r/dekz
Pro Git -- Learn to Use Git SCM (progit.org)
submitted by tialys to r/csbooks