None of my friends know how to do this, and I saw it being done by a cover band but still don't understand.

Its this scream you do using your fretting fingers, and it can be done at the top of the fretboard. It seems like you bend a harmonic, but its really loud, clear, and screaming. I don't think its pinch harmonics, but I haven't learned it so I don't know. I believe its a common technique, so please help me out.