Pants are apparelbottoms that have material which covers the entire leg, down to the ankle.
About Shorts:
Shorts are apparelbottoms that have material cut short above the knee or slightly below the knee.
About Swim Shorts:
Swim shorts are lower body garments used for sunbathing, swimming, or any other type of water sports activity. Swim shorts are made from a wide variety quick-drying materials, are generally loose-fitting, and feature a brief-like design.