Polyester is a type of fabric made from synthetic fibers created in chemical laboratories rather than grown on farms or harvested from animals. Unlike cotton (which comes from plants) or wool (which comes from sheep), polyester is made from petroleum, the same crude oil used to make gasoline and plastic.

Scientists invented polyester in the 1940s, and it quickly became popular because it has some remarkable properties. Polyester doesn't wrinkle easily, dries quickly after washing, and lasts a long time without wearing out. Many athletic clothes are made from polyester because it wicks moisture away from your skin, helping you stay comfortable during sports. School uniforms, winter jackets, and even some carpets contain polyester.

The downside is that polyester doesn't breathe as well as natural fabrics like cotton, which can make you feel warmer or stickier on hot days. Many clothing manufacturers blend polyester with cotton to get the best qualities of both: the durability and wrinkle-resistance of polyester combined with the breathability and softness of cotton.

When you check a clothing tag, you'll often see “100% polyester” or “65% polyester, 35% cotton.” That percentage tells you how much of each material the fabric contains.