Git is a distributed version control system that's free and open source and designed to handle everything from small to very large projects with speed and efficiency. People use it to work together, using the same files, and helps a team to edit the same file. This way many people can have their version of the file local and all see who is changing and doing what. This helps mitigate any confusion as changes happen. While you may prefer to work on the command line, there are GUI clients for Git you can buy or download for free.