A Question Of Power

I've been looking at stepper motor product tables and notice different
descriptions for amp ratings. I have no actual experience with
steppers and wonder if anyone can tell me:

1.a] Do Amps and Nameplate Current Rating represent the same thing?
1.b] If not, what is the mathmatical relationship between them?
2.a] Are Amps and Amps Per Phase equivalent?
2.b] If not, what is the mathmatical relationship between them?
3.} For these two types, are Amp ratings equivalent to those of Center
Tap, Half Winding (for 6 Lead) and Parallel (for 8 Lead) connections?