Polyester is an umbrella term that describes a manufactured fiber whose substance is any long-chain synthetic polymer, where at least 85 percent (by weight) of the polymer is an ester and terephthalic acid. Most polyester is made of polyethylene terephtalate. The properties of polyester fabrics vary depending on their composition, web structure and processing, but some general features are found with nearly all polyester fabrics.
Polyester is a strong and durable synthetic fabric. Polyester dries quickly and can be washable or dry clean only. Polyester is often used as a blend with other fabrics to lend wrinkle resistance. It is not the easiest fabric to remove stains from, and doesn't breathe as well as other fabrics may.
Fabrics woven or knitted from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets, upholstered furniture and computer mouse mats. Industrial polyester fibers, yarns and ropes are used in tire reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption.
Sources: Ehow, Wikipedia