Labels vs. Branches

I'm trying to get the Vault model into my head, so we can evaluate how best
to use its features in our environment. In particular, I'm stuck on the
differences between Labels and Branches. One of your white papers says

"An important thing to realize here is that in every way that matters, a
Label and a Branch are the same thing."

OK. So what is the difference? When would I use one vs, the other?

.Mike