Initialism for the Science Fiction and Fantasy Writers of America, a mutual-aid organization for pro authors, originally named just Science Fiction Writers of America. The acronym is pronounced "sif-wa" or "sef-wa" and, despite the name change, the initialism remains SFWA with only one F.
Unlike writers' groups such as the Romance Writers of America, which welcome wannabes, to join SFWA, a writer must have sold at least three short stories or a novel at a word-rate set by SFWA.
SFWA was founded by Damon Knight, among others, in 1965. Since Damon's "Unite or Fie!" article in an early Art Widner fanzine has often been credited with provoking the establishment of the National Fantasy Fan Federation a.k.a. the N3F, there were those who wondered why he hadn't "learned better" the first time….
It has been a tumultuous group, but that's a story for Procyclopedia. (See http://www.sf-encyclopedia.com/entry/sfwa)
Worldcons usually provide SFWA with a free hotel suite in which to hold a weekend-long not-so-secret pro party. Nobody knows why fans should pay for this bonus to filthy pros when we aren't allowed in, but it's a tradition. Prosuckers will do anything to get into the SFWA Suite, but it's usually not worth it, being big on neopros and short on refreshments.
Contributors: Dr. Gafia, others.