The sport of Cyclocross racing pits riders and bikes against tricky terrains, rough dirt and rock paths, precipitous drops, barriers both natural and man made, and hopefully some mud!
Cyclo-cross bicycles are similar to road racing bicycles in that they are lightweight, with narrow tires and drop handlebars. Where they specialize is with lower gearing, stronger frames, greater tire clearances, cantilever brakes, and a more upright riding position. Like mountain bicycles, they are likely to be equipped with knobby tread tires for traction and, increasingly, disc brakes. They have to be lightweight because competitors need to carry their bicycle to overcome barriers or slopes too steep to climb while in the saddle. Therefore, the rider dismounts and carries the bikes over these obstacles.
Cyclocross designed bikes are sometimes making into more general use because they offer a rugged bike that is lightweight and can handle off-road conditions.