Brass instruments are usually made of brass and have a round mouthpiece. The instrument itself is like a long metal pipe, wound around into a shape that makes it easier to play. The player blows into the mouthpiece, but at the same time making a buzzing sound with her lips.
Most brass instruments (trumpets, trombones and French horns) are played with the help of valves that open and close holes to change the pitch. The trombone, however, uses a slider to change notes.