Can someone explain to me what the groups are ie. group N etc

What cars can race in what class, up to what power output or however it works?

mmm not much is coming up:

Group A, the race and rally category for production-based cars, called for a production run of 5,000 cars.

Group B, which would be the formula used in World Championship rallying, required a run of just 200 cars – and of those, 20 cars could be further modified into an ‘Evolution’ specification - http://www.stormloader.com/groupb/

Group N - http://www.rallysportmag.com/cms/A_105047/article.html http://www.deficarsport.com/groupnroad.htm

Group S - http://www.stormloader.com/groupb/s.html

duno if that helped?

thanks, thats cleared it up