I found it pretty helpful with the use of the word "tree" (got it from http://progit.org/). But I definitely need to add some kind of glossary to the page.
Thanks for your feedback! I completely understand your point. Maybe it would make sense to make another guide with an intro on Source Control Management systems and link it in the git guide. Currently, you need to have a little bit of knowledge on an SCM. But I will think about it.