LOL means "laughin' out loud"..you can use it anytime you find / read something funny or hilarious or if you make a sarcastic remark and you don't want others to find it offensive...You can even make your reaction seem more intense by typing ROFL or LMFAO ;P

LOL: "laugh(ing) out loud". You could use it at the end of a statement to indicate that you think your own comment is funny, or even to reassure the recipient that your comment is just teasing. For example: "wear r u? your n idiet lol" Make sure the standard of your English is dropped to an appropriately sub-literate level if you decide to use this.

i think "lol" is another way when you say "ha ha ha" you know lol=laugh out loud, it is like chinese "捧腹大笑" it's just my personal opinion

use it whenever you find something humorous. There are no rules because it's just internet slang