What are the benefits of version control?
Version control is beneficial because projects are often being worked on by multiple developers, creating the risk of one developer overwriting the work of another, or data loss. Version control minimizes the risk of data loss by creating branches that each developer works on, eventually merging their work into the 'master' when it is ready. By separating each developer's work into branches, the risk of data loss is minimal.
How does git help you keep track of changes?
The use of branches helps you keep track of changes in git. When you create a branch, you have a clear point that you can easily reference as your 'jumping off point'. Then, while you are working on your branch, you add and commit changes as often as you like, creating more points that you can return to if something ends up going wrong.
Once you are done with your work and have pushed it up onto GitHub, changes are tracked via pull requests. This allows other people working on the project to view your work and be aware of it before it gets merged into the master branch.
Why use GitHub to store your code?
Storing code on GitHub fosters easy collaboration during the course of a project, and provides an easy and logical way to track changes as a project evolves. It also provides an open source environment where developers can find your source code if it could be useful for other projects.
Also, here's a link to GitHub's Git cheat sheet, for handy reference!