When programmers talk about source file control systems they most often talk about Git. If you have one person writing a paper, it is easy to track the changes and differences. But imagine you had 10 people writing the same paper. And it wasn't real time (like Google Docs). How would you track which changes affect which changes and which is the most current state of the paper?
Git is a version control and source code manager. You can use it as much or as little as you want. Basically it saves snapshots of your work and provides tools to ensure that the version you are working on is the most current version and the changes you are making are not negatively affecting someone else.
That being said, at the moment I find Git hard to use.
(This is the Git UI. Terminal. Command line.)
There are various project and sites and tools to make Git easier to use (see Github.com). Github for Mac seems like a good place to start. I will report on how it goes soon. Until then… party on!