How do those on YouTube separate their camera from the action?

I'm sure everyone has seen many YouTube clips from various scenarios/set-up's where they seem to have the camera about to move all over the place, and/or have a camera location set up and see car's in the distance coming towards a situation that's been setup as where all the action (crash) is about to happen.

How do they do that?

 

I think they just create a replay, and then make a camera path with world editor (f11) or they just use free camera instead.

 

Thanks.
Does anyone know if there are some tutorials about how to "set up" scenarios, how to tell cars what do you, and how you get put things on motion and then use a camera to watch the event freely?
It sounds fun, but I've no idea how to even start

 

to begin/stop replay you need to press f2 (in my case at least)
Camera Path tutorial:


AI path tutorial:

 

Thanks for that, I'll take a look and have a play