of course you know dummy .. you wake up with cum all over your boxers. .
it is when you havent masturbated or released semen in a long time so it has built up, and has to be released some how: a wet dream. I have personally never had one because i masturbate so frequentley . .
hey another eason to masturbate!
and you will usually wake up remembering a very nice erotic fantasy .. you basically had sex for 7 hoursin your sleep but didnt orgasm