Sun tanning is the process whereby skin color is darkened or tanned. The process is most often a result of exposure to ultraviolet (UV) radiation or the sun or from artificial sources, such as a tanning bed, but can also be a result of windburn or reflected light. Many people deliberately tan their skin by exposure to the sun, called sun bathing, or by the use of artificial tanning methods. Some people use chemical products which can produce a tanning result without exposure to ultraviolet radiation.
Moderate exposure to the sun has a beneficial impact, including the production of vitamin D by the body; but excessive exposure to ultraviolet rays has detrimental health effects, including possible sunburn and even skin cancer. To avoid sunburn, most people apply suitable sunscreen to skin exposed to the sun.
Some people tan or sunburn more easily than others. This may be the result of different skin types and natural skin

A suntanned arm showing browner skin where it has been exposed. This pattern of tanning is often called a Farmer’s tan