Including but not limited to; the (often unnecessary) abbreviation of words, acronyms special characters (@,~), numbers (l33tsp33k), *actions*, /me command, "ooc" and other RP references, emotes, ASCII, Real or Pseudo Programming Code, and HTML tags
The recent popular use of text messaging on cell phones seems to have made the shortening of words much more common than ever before.
Also: netspeek, netsp33k, n37sp33k, and other variations.
i g2g to da stor 2day c ya l8er LOLZ
i @m 5o 1337 i pwn joo
Useful: Uh oh, I have to go answer the phone. BRB.