ure is a shortening of the word "you're" as in "You're murdering my language sir".
It's often used interchangeably with the term ur. Technically though there is a difference between the two. ur is a shortening of "your", as in "I see your dictionary is still in the shrink-wrap sir".
DaBombdaH00d:UR DA NUB. ur having red wine with teh garden salad. LOLOLOLOLOLOL. OMFG M8!1!
<Literacy has left the restaurant>