Pro Git, Scott Chacon, Ben Straub, 2014 (Apress) - The official, comprehensive guide to Git. This chapter explains the core concept of branches as lightweight pointers to commits.
Git Branching, Atlassian, 2024 - A widely recognized tutorial that clearly explains Git branching concepts, including the pointer analogy and common workflows.
Lecture 5: Version Control (Git), Anish Athalye, Jon Gjengset, and Jose Javier Gonzalez Ortiz, 2020 (MIT OpenCourseWare) - Part of a well-regarded MIT course, this lecture provides a fundamental explanation of Git, including its branching model.