If you are a developer or have even the slightest interest in programming, you need to learn about Git, a free software version control system that is widely used by Mac and iOS developers to keep track of changes in their code and to allow teams of developers to work on the same chunk of code.
Git is useful for non-developers as well. Git will track just about any sort of file, and will let you share those files with other folks on your team.
If you are still with me, take a look at this Git tutorial from Code School. I found it extremely easy to follow and very well done. You’ll be typing commands in a mocked up terminal window, so you’ll be learning the commands at the heart of Git. There are plenty of tools out there that wrap these commands in buttons and menus, but this tutorial really gets you into the foundation of Git.