musical scale pattern

I've heard various music patterns, I was listening to Saturn (Holst' Planets) and the first section of the piece has two themes with different instruments and they sound like they don't go together but it works. What is that called?
Jan

counterpoint?

Yeah, counterpoint, probably.

What would using counterpoint serve?
Jan

Sorry - I'm not quite sure I understand the Question.

all about counterpoint here http://en.wikipedia.org/wiki/Counterpoint

Thanks NEB, I understand it better.
Jan