Tulle is a type of fabric that's a stiff, fine netting and is often used to make gowns and wedding veils. Any dress for a formal occasion — a wedding, a bat mitzvah, a quinceañera — might have a tulle skirt.
Tulle is most often made of manmade fibers like polyester or nylon, but it can also be made from silk. It comes in just about every color, and it's commonly used in wedding dresses and ballet tutus. The word tulle comes from the name of the French town where the fabric was originally made in 1817, Tulle.