Lol

Lol mean "laugh out loud" it's often used while texting, if someone texts you something funny you can say "LOL" meaning that you find it funny. It's also used many times on social media platforms such as Twitter, Facebook, Instagram etc.

John: "Wanna hear a joke?"
Kevin: "Sure"
John: "What's big, green and sits in the corner?"
Kevin: "What?"
John: "THE INCREDIBLE SULK!"
Kevin: "LOL"