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".
PsychoSlayer44: omg m8!!! ure havin ure steak wit teh white wine!!1! URE TEH WINE NOOB!! WTF?!?
DaBombdaH00d:UR DA NUB. ur having red wine with teh garden salad. LOLOLOLOLOLOL. OMFG M8!1!
<Literacy has left the restaurant>
Abbreviation on the internet for the word "You're" that is generally used when you don't have many available characters left to get your point across. While for the most part staying gramatically correct.