While playing online video games players like to kill one another.
When you kill some one repeatedly you "own" them.
"P0wned" became a net term for this,
and is an abbreviation of "P0wned" is "pwn".
Pwn is an insulting way of saying you own someone.
Pwny club (Pony Club) reads like it sounds and is used to be futher insulting.
*Chard Kills Gunslinger*
CharD: I owned you.
Gunslinger: You're gunna get P0wned.
An online phrase used in an insulting or derisive manner towards someone that you have just badly beaten or "schooled" in some manner, similar to telling someone annoying to enjoy a glass of shut the hell up.