some times used to show amusement.
sometimes used to show that what the person is saying, doing, trying to do,or asking is complete unresonable on your standards.

Like lol, it is meant to convey a laugh in texting and instant messaging, but unlike lol, you must actually have laughed before typing it. It also implies more confident laughter.

Basically it's a way to say lol, without having to say lol. It's great.

An interjection sometimes used when backdating an unwritten post while writing a month long blog about your reading of David Foster Wallace's Infinite Jest. It simultaneously expresses the poster's regret for not having written and also glee for having gotten away with it.