GIT is an open source version control system that runs best on unix machines, but is also available for windows.

Software developers are constantly tracking changes to their file system so that any false steps during the development of a software product can be reverted. Git allows you to snapshot your current work and to query to see what has changed since your last snapshot. The tool is used via the command line, but there are GUI versions available. To those unfamiliar with software development, this all may sound quite strange, but to an average computer user this capability is quite useful. For example, suppose you are editing an HTML document, and you’d like to try out an alternate version. Simply use git to snapshot your work, then continue writing. If you don’t like your changes, you can simply revert to a previous revision. You can also use git to push and pull changes from remote machines in order to collaborate with other users of git around the internet or you work team.