Person 1: LOL, earlier Joey fell off his skateboardin the middle of a kickflip, and yet he claims he would've been able to do it.
Person 2: LMAO, that dumbass can't even ollie.
'lmao' is an Internet slang, meaning laughing my ass off. It is not considered an 'official' word, and can be associated with the words 'lol' and 'rofl'. It is generally known as a stronger version of 'laughing out loud'