What uses a fuel dampener and what for?

[davepl]

I saw a reference to "fuel dampener vs fuel regulator" in another post, didn't want to randomize that thread, so:

What's a fuel dampener for, what cars have one?

I'm assuming it takes out (absorbs) the pressure drop pulses from injectors firing, but since lots of cars don't have one, curious about when they added them, to what they added them, and so on. I know nothing, tell me everything!