This article covers the basic data format Git uses internally and explains how the staging area works. It's a good primer for those looking to have a little bit deeper understanding.

If you like this article and are looking for a much more in-depth understanding of how Git works, I recommend Jim Weirich's Source Control Made Easy series.

http://pragprog.com/screencasts/v-jwsceasy/source-control-ma...

Unfortunate article name since the content is more interesting than it suggests!