T-shirts are typically made of cotton fibers (sometimes others), knitted together in a jersey stitch that gives a T-shirt its distinctive soft texture. T-shirts can be decorated with text and/or pictures, and they are often used to advertise (see human billboard), promoting products, companies, films and websites.

T-shirt fashions include many styles for both men and women, and for all age groups, including baby, youth, teen, adult and elderly sizes.

The T-shirt evolved from undergarments used in the 19th century, through cutting the one-piece "union suit" underwear into separate top and bottom garments, with the top long enough to tuck under the waistband of the bottoms. T-shirts, with and without buttons, were adopted by miners and stevedores during the late 19th century as a convenient covering for hot environments.