A lot of what we do involves writing code in some way. When you write code, especially in a group project but even when on your own, it is SUPER-useful to do some kind of source code management (SCM) -- basically, this means using a tool that keeps track of the various changes that different people are making to the code base. Even when only one person is writing the code, SCM helps you keep track of what you have changed since the last "stable" version of your code; anyone who has done a significant amount of programming will be aware of how crazy things can get when you lose track of what you have changed since the last time the code actually worked like it was supposed to.
Anyway, the SCM tool we mostly use is probably also the most common one nowadays, namely Git. If you are using a Mac, which you should be if you are in this lab, you already have Git pre-installed. If you are using Linux, you probably have it too (or you are a big enough nerd that you already know how to install packages and can easily do so). If you are using Windows, may God have mercy on your soul.