A collection of terms, often unique to any one person's vocabulary, that orginated online. Used to express actions, or to abbreviate often used but long phrases. Examples include: IMHO, IMNSHO, IRL, LOL, LMAO, ROFL, BRB, a/s/l, wb, AFK, BBL, BBS, PHB, TTFN, RTFM, TLA, SOB, SOG, FYI, IDIC, NP, YW, BBIAB, WYSIWYG, TMTOWTDI, OOB, L8R, IANAL, FAQ, FUBAR, BTW and my personal favorite, WTF. The sign of a true Net addict is the use of Netspeak IRL. Overuse of Netspeak is often associated with AOLers and/or 31337 hax0rs/script kiddies, such as use of "u" for "you", and substitution of numbers for letters.
Netspeak can also take the form of actions enclosed in either asterisks, colons, or prefaced by slashes, e.g. *laugh*, *eyes*, or *ponder*. These actions often orginate on MUDs or other role-playing games, though not always.
Finally, smileys are faces made of ASCII type (no, I'm not going to list them all, thats a task for another node), the most basic being :) and :(
Thanks to all (especially THEWeirdo, man you know way too much Netspeak, but thanx :) ) who suggested netspeaks, and please feel free to writeup your own.