Tan has two main meanings:

1. A golden-brown color that skin turns after spending time in the sun. When ultraviolet light from the sun hits your skin, your body produces extra melanin (a natural pigment) as protection, darkening your skin tone. Someone with a tan might have spent a week at the beach or worked outdoors all summer. The word works as both a noun (you have a tan) and a verb (your skin tans in the sunshine).
2. A yellowish-brown color, like leather or certain shades of khaki pants. You might paint a room tan if you want warm, neutral walls. Tan sits between brown and beige on the color spectrum: darker than cream but lighter than chocolate brown. Animals like deer or camels often have tan fur, which helps them blend into dry grasslands or desert sand.

As an adjective, tan describes something that has this color, like a tan jacket or tan paint.