The about section is mostly a guide to understanding Git and its features. It also shows benchmark tests on multiple different operations, comparing itself to Subversion.
The downloads section allows you to download Git, but also shows GUIs from multiple different clients, including licensing, price, and platforms. It also has a page to download different Git logos if you needed them.
The documentation page includes reference manuals which can help teach you how to use Git and set up your own repository, and is a deeper guide to learning about Git. It also gives you the online Pro Git book for free, and has videos to teach you the basic of Git.
This section includes the entre Pro Git book written by Scott Chacon and Ben Straub. It involves updated corrections from hundreds of contributors, and can be changed if there is an error or suggestion.
This website has everything you need to know about Git. You can learn from a publicly updated book, watch videos to get an understanding, or learn how to create and do things on your own repository. There is also a list of all the Git commands.