Circuit Board Abreviations
Depends...

You are asking about "reference designators."


There are well-applied "standards" (see below)
Companies and fabricators often apply their own permutations to the standards
I personally see a trend towards more descriptive reference designators from clients made possible, in part, by cheaper access to better legend writing (silk screening) processes. When you can write ever smaller letters more legibly, there is pressure to make use of the capability to reduce confusion on the rework and assembly lines. 
Wikipedia has a nice summary of the designators in MIL-STD-16 (It's the same list available in CircuitHub's schematic symbol editor).


(My) Summary of the Codification History:

1950's Military defines standards for drafting to facilitate what we now call "lifecycle management"

1970's IEEE/ANSI tries to get in on the action and set a wide reaching commercial standard

1990's IEEE tries to update it, but realizes its pointless (e.g. good enough)

From Wikipedia (emphasis mine): 


  IEEE 200-1975 "Standard Reference Designations for Electrical and
  Electronics Parts and Equipments" is a standard that was used to
  define referencing naming systems for collections of electronic
  equipment. IEEE 200 was ratified in 1975. The IEEE renewed the
  standard in the 1990s, but withdrew it from active support shortly
  thereafter. This document also has an ANSI document number, ANSI Y32.16-1975. This standard codified information from, among other
  sources, a United States military standard MIL-STD-16 which dates back
  to at least the 1950s in American industry.