I dont understand what author is trying to say. I always understood branch as just a pointer on a linked list of commits. You can freely move around this pointe

I dont understand what author is trying to say. I always understood branch as just a pointer on a linked list of commits. You can freely move around this pointer. Head is similarly another pointer to the current commit. This plus each commit is contains whole file which was changed in that commit. Is author saying the same thing or is he saying that each commit also has some hard-coded reference to the branch in it too?