GIT is a widely used source code management system for software development. It was designed and developed in 2005 by Linux kernel developers (e.g. Linus Torvalds) for Linux kernel development.
GIT is a distributed version control system with complete history & version-tracking capabilities. [Other version control systems you may have heard of are Subversion, CVS, Perforce, and ClearCase]
GIT is FREE & distributed under the terms of the GNU General Public License version 2. More @ https://git-scm.com/