1337 = LEET, pronounced either like it's spelled, or 'EL-EET' (i.e. 'Elite'). Basically, some numbers and punctuations can be used to look like letters, and, as such, they're used to say things and look k3\/\/1 (kewl -> cool). This is Leetspeak.
Pwned/Pwnd: came from the common problem of...