To correct minorly, it's actually GFCI and AFCI, Ground Fault Circuit Interrupt and Arc Fault Circuit Interrupt.
Seems like standard housing code is for AFCI in bedrooms post 2002, which is not your standard christmas tree location.
A summary, w/ cute animation:
http://homeworksinsp.com/electrical.aspx
... and, elsewhere,
some cynicism about the tangible difference between an AFCI circuit breaker and a GFCI ... and, here,
a lengthy explanation of history, function, and purpose.
I say, turn your lights off at night.