Is web browser JavaScript runtime?

In Node.js website, they say Node.js is a JavaScript runtime.

Are web browsers like Chrome, Firefox, Edge, ... JavaScript runtimes?

I thought of course, web browser is JS runtime. But I'm confused, In this video 12:10~ He says Web browser is not just JavaScript runtime because it can do more things at one time, it can give us other things.

But I think V8 engine only can do one thing at one time, while JS runtime can do more things than one at one time.

Am I wrong?