No. There are leaves that aren't heads (for example, after you delete a branch, the old commits just lie around until someone deliberately cleans them up), and there are heads that arent' leaves (for example if you branch a new feature branch from main. The feature branch brances off of main, so main is not a leaf anymore)

> The feature branch brances off of main, so main is not a leaf anymore)

But "main" remains a "head" even though the feature branch "continues the graph" from it?

So there must be a difference between "Adding a new commit" and "Branching a new commit". I think I got it now. Thanks

There’s no “branching a new commit” (except as syntactic sugar). Creating a branch creates a new head pointing to an arbitrary commit (even one that already has one or more heads). Committing creates a new commit and moves exactly one head forward to it.