well its D for deluxe P for premium s x or performance
those are the components
somemodels share different plattforms D and P with the same ( or similar) frame
like the Speed D 7 and the Seed P 8 ... simplified the D7 has 7 gears a steel speed frame and deluxe components .. the Speed P 8 has the same steel frame but premium components ..

and so on ... complicated ? call me

thor