the parallel path is an equivalent circuit description
In a lap winding, the number of parallel paths,a, is always equal to the number of
poles,p, and also to the number of brushes.
In wave windings, the number of parallel paths,a, is always two (2), and there may be two or
more brush positions. Wave winding are more suited to high voltage low current applications if memory serves correct. vice versa for lap High current, low voltage
edit looks like there's been some changes since I looked at DC windings, not surprisingly.