Pants are apparel bottoms that have material which covers the entire leg, down to the ankle.
About Riding Chaps:
Riding chaps are leg coverings, usually extending from the ankle to the knee, designed to provide grip and lower leg protection to the rider during horse shows, performances, or while pony trekking. Riding chaps are usually made of leather and have a zipper or hook-and-loop closure on the outside. Riding chaps are widely worn by children in equestrian competitions.
Shorts are apparel bottoms that have material cut short above the knee or slightly below the knee.