For simplicity's sake, I call any letter abbreviation of a multi-word name an "acronym." But that's not technically correct--there are two different types of letter abbreviations: acronyms and initialisms.
To put it simply, an acronym is an abbreviation that is pronounced as a word:
-DOMA (Defense of Marriage Act)
-CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act)
-SWAT (Special Weapons and Tactics)
An initialism, on the other hand, isn't pronounced as a word. Instead, each letter is pronounced individually:
-CIA (Central Intelligence Agency)
-ACLU (American Civil Liberties Union)
-RFRA (Religious Freedom Restoration Act)
There also are some words that appear to be a combination of an acronym and an initialism:
-GDOT (GA Department of Transportation)--pronounced Gee-dot
According to The Bluebook, entities with widely recognized initials may be abbreviated without periods (i.e. DOMA rather than D.O.M.A.) in both case names and in-text references. R. 6(b).