Tanning works the same way indoors and outdoors. Ultra violet light penetrates the skin, increasing the production of melanin (the tanning pigment).
UVA rays are sometimes called the tanning rays and UVB the burning rays. Indoor tanning processes are filtered, emitting more UVA and much less UVB than the sun, making it a much preffered option for many people.
Sunbeds have many clinically proven benefits as they enable the production of vitamin D which is essential for good health. For more information about this please visit The Sunbed Association's official website: