A distributed version control system (DCVS). Git provides a distributed development, giving each developer/user a local copy of a repository, which includes the entire revision history. Changes are copied from one repository to another. Branching and merging are easy to do. Users are not dependent on network access or a central server so Git is very fast and scales well when working with large projects. It provides cryptographic authentication of history and offers tools for both easy human usage and easy scripting to perform clever operations.
GNU RCS (Revision Control System) is an open source revision control system for text files, source code, programs, graphics, and other documentation. It stores, tracks, logs, identifies and merges versions. Development continues as a volunteer effort under the Free Software Foundation.
Mercurial is a free, distributed source control management tool and is used for version control of files. Mercurial is distributed, giving each developer a local copy of the entire development history.
SVN (an abbreviation for "subversion") is an open source version control package of the Apache Foundation. Version control is a process whereby: 1) versions of a document are saved for later retrieval, even if the document is later deleted; 2) versions of a document may be compared for differences; 3) multiple authors may edit and build the document version chain, with software support for avoiding, managing, and resolving collisions; 4) catastrophic failure recovery mechanisms are in place to maintain document and version integrity across a wide class of possible threats.