What is FBWA/FBWB mode?

Going through the initial setup instructions, and don’t know what it means? Is there a glossary of terms anywhere?

FBW means “Fly By Wire” and the A and the B are the different versions. I believe FBW is where the APM keeps the plane level (a sort of assisted flying) without the operator having to provide any R/C input.
Try the Wiki here: http://plane.ardupilot.com/wiki/flying/flight-modes/#FLY_BY_WIRE_A_FBWA
TCIII Developer

Thanks, I had not read ahead and that answered many questions when I did