Motocross is a bit different it includes a set track that riders race around.The track is made of mud/dirt.The reason is so that if the riders come off then the dirt wont hurt them that much. Another reason is that the dirt is portable. Here are some images of motocross.
Riding motocross is fun because of all of the dirt jumps built in to the track. The track has things called whoops these are little diverts in the track to make it more interesting.Here are some images of whoops.
My favorite freestyle motocross riders are,
Blake Bilko Williams
Cameron Sinclair