a.k.a. conversational abbreviations, acronyms, abbreviation, alphabetism, initialism, shorthand, text message shorthand, text messaging shorthand
Derived from the first letters of a phrase, acronyms are meant to make the phrase easier to say and remember. With an acronym, the first letter of each word makes up a new word that is, in fact, pronounceable (for example, SNAFU is pronounced "sna-foo" and WOMBAT is pronounced "wahm-bat").
Acronyms have been an integral part of computer culture, and many
originated in the military and government sectors. The use of acronyms
grew rapidly on the Internet and created a new lingo, known as
shorthand. Shorthand, also known as alphabetism, is when you say the letters one-by-one and not
pronounce it as a word (for example, FYI is pronounced "F-Y-I" and BRB
is pronounced "B-R-B"), and an initialism is when you reduce a word to it's initial letter (such as v for very).
One of the reasons why acronyms and shorthand became so popular so quickly in the online world is because they are fun to use and because they take less time and effort to type. If you are texting, IMing or chatting, it is often quicker and easier to type a few well-known letters than to spell out the whole phrase. And for some millenials, it's considered kewl to communicate in a lingo that not everyone knows (even though other generations use acronyms too ;-)
There are, of course, exceptions. For example, some acronyms go both ways (such as FAQ, which can be pronounced "fak" or "F-A-Q"). It should also be noted that acronyms are generally typed IN ALL CAPS (not to be confused with SHOUTING) whereas some forms or shorthand are typed in a lowercase see some lowercase examples here.
For the largest list of Internet acronyms and text message shorthand, click on "more info" below!