Somebody explain spotting to me. If I'm a scout and I use the binocs, do I have to press any key to get "send the spot" to my artillery guys? Does the "spot" go out to everyone in an artillery vehicle, out of range or not?

How does this "spot" work? Is it a spot in the sky for them to fire at or what?

I'm asking because I have never been able to get anyone to cooperate with me in a net game, and it kinda doesn't work in Solo... :P