Git is a distributed version control system, first released in 2005 by Linus Torvalds. One of its main advantages over traditional version control tools (for example, SVN) is the ability to maintain versions without a centralised server. A local GIT folder is already sufficient to be fully fledged repository, with the entire version history. A very smart and compact way of handling code history allows programmers to switch between development branches in seconds, even on very large projects.
GIT's simplicity and ellegance add a lot of new use cases over just source code control. There are numerous tools for notes handling, journalistic work, recipes' storage and modification, legal documentation collaborative work and even music writing, that use GIT as the underlying technology.