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.
Projects which use Git include Git, Ruby on Rails, Eclipse, Android, and Perl to name a few.