A version control system is a program that can record multiple versions of a source file, storing information such as the creation time of each version, who made it, and a description of what was changed.
The Emacs version control interface is called VC. VC commands work with several different version control systems; currently, it supports GNU Arch, Bazaar, CVS, Git, Mercurial, Monotone, RCS, SCCS/CSSC, and Subversion. Of these, the GNU project distributes CVS, Arch, RCS, and Bazaar.
VC is enabled automatically whenever you visit a file governed by a
version control system. To disable VC entirely, set the customizable
(see Customizing VC).