This essay from Mary Rose Cook explains how Git works. Who should read this? Anyone who wants a deeper understanding of Git.
The essay assumes you understand Git well enough to use it to version control your projects. It focuses on the graph structure that underpins Git and the way the properties of this graph dictate Git’s behavior. Looking at fundamentals, you build your mental model on the truth rather than on hypotheses constructed from evidence gathered while experimenting with the API. This truer model gives you a better understanding of what Git has done, what it is doing, and what it will do.
(If you’d rather absorb the same information as a talk, you can watch this video instead.)