All brass instruments are played by placing the lips on the mouthpiece and making a buzzing motion, while blowing air. The wind vibrating through the instrument, along with the compression of the valve stems makes the sound that the brass family is known for.
Brass instruments are not always made of brass. They are made from wood, bones and other metals. The first trumpets were actually conch shells.
No matter what they are made of, brass family instruments have a cup shaped mouthpiece, the coiled tube that leads to a flared horn at the end. They all have valves. The slide on the trombone works like the valves on the other brass instruments.
Although they can be made from brass, a piccolo, flute and clarinet are not a part of the brass family. A saxophone is also not a part of the brass family. All of these instruments are woodwinds.
Brass instruments are also called aerophones because of the way air moves through them to create sound.