a.k.a. email shorthand
The acronyms or shorthand used in online chat, e-mail, instant messaging, blogs or newsgroup postings. This shorthand represents the most common phrases people type to each other, making them quick and easy to type instead of the full phrase or sentence.
Some of the earliest shorthand terms were: IMHO (In My Humble Opinion), BTW (By The Way), RTM (Read The Manual), LOL (Laughing Out Loud), FWIW (For What It's Worth), ROTFL (Rolling On The Floor Laughing), and WYSIWYG (What You See Is What You Get). Now there are thousands of shorthand terms, click on "more info" below!
BTW: If you ever see AN ENTIRE SENTENCE IN ALL CAPITAL LETTERS, it implies that someone is SHOUTING. This not appropriate netiquette, in fact, a woman got fired for typing in ALL CAPS in 2009, see the Yahoo Tech News article below!
NetLingo Classification: Online Jargon