Sweat (perspiration) is the salty fluid excreted by the body's sweat glands. It passes from the sweat glands through the skin's pores. Sweat is a watery solution containing sodium chloride (salt) and urea. The primary purpose of sweating is the regulation of body temperature. Typically, one sweats when exercising or overheated, but nervousness can prompt sweating as well.
Sweat may act as an irritant if it comes in contact with a fresh piercing, tattoo, or other body modification, so it may be advised that you not exercise for a day or two after any of these procedures.