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. In Git, you can have your own local repository and nearly all the operations in local.
Every Git clone is a fully-fledged repository with a complete history and full revision-tracking capabilities, which are not dependent on network access or a central server. Branching and merging are fast and easy to do.
Git is used for the version control of files, much like tools such as Mercurial, Subversion, CVS, Perforce (http://git-scm.com/).
Git was initially designed and developed by Linus Torvalds for Linux kernel development.