:lol = I laughed for real. I still respect the term and use it how it should be used. Serious business.
"looooooooooool" or "LMAO" or "I'm dying" or "lololololol + random keyboard mashing" = I'm laughing hard, possibly to the point of tears, and/or people around me think I'm crazy.
Fun fact: Random keyboard mashing can also be a sign of frustration. It takes a professional to used it correctly.
"Heh" = Short, kinda sarcastic filler chuckle. Can be used in a bunch of different ways, usually when someone says something I really disagree with, and I'm about to drop a bomb on them.
I've thought about this too much, and will be too self aware when using the terms now. Thanks, Spring-Loaded