LOL is Internet slang for "Laugh Out Loud". LOL has been in use, especially on chat, since over a decade.
Lulz is relatively newer Internet slang, that originated as the plural variant of LOL. LOL is usually read "ell-oh-ell" but when you pronounce it as a word, it can be read as "lul". The plural for this is "lulz" (several Internet slang plural forms use Z instead of S).
Lulz is typically used as I did it for the lulz or IDIFTL - which is a catch-all explanation for any trolling or any internet drama you cause, harrassing some Internet users for the amusement of other users.
This has been pioneered by Encyclopedia Dramatica, famous for posting a fake craigslist ad and then listing the personal info of those who responded. Their slogan is "In lulz we trust".
|Meaning:||"Laughing Out Loud" or "Lots of Laughs".||Derivative for "lol", usually associated with trolling others in the internet.|
|Commonly Used:||Text messages||Forums, chats|
"Lol vs Lulz." Diffen.com. Diffen LLC, n.d. Web. 20 Nov 2014. < http://www.diffen.com/difference/Lol_vs_Lulz >