Git is version-control software that allows you to keep an archived copy of your project each time you save it to Github. This means if you make a mistake, you can "revert" or roll back your project to before the mistake was made, and try it again. As you can imagine, this comes in very useful sometimes :)
Git has a special set of commands that you type in the Command Line that let you create new projects, save and remove files, and add notes so you remember what changes you made. Below are some great guides to help get (git, hahaha) you started with the basic commands:
Git - The Simple Guide - Roger Dudler
Very simple, straightforward commands and instructions, great for reference.
15-minute tutorial on how to use Git, featuring OctoKitty!
A Non-Programmer's Introduction to Git - Scott Lowe
If you're looking for deeper explanations of all things Git, this is the place to go. Complicated concepts, layman's terms. Includes links to other great tutorials as well.
Git Reference - Github
The official reference guide created by Git and maintained on Github Pages.
If you find another resource you enjoy, let us know! We'd be happy to link to your recommendation as well.