A large musical ensemble consisting predominantly of brass, woodwind and percussion instruments.
Wind bands are also commonly referred to as a concert bands or wind orchestras, amongst other names. The ensemble is predominantly made up of brass, woodwind and percussion players, although a string bass is a common feature, and more occasionally harpists and pianists may be found.
A standard orchestration would be as follows:
Piccolo
Flute
Oboe
Eb Clarinet
Bb Clarinet
Bass Clarinet
Alto Saxophone
Tenor Saxophone
Baritone Saxophone
Bassoon
Trumpet
French Horn
Euphonium
Trombone
Tuba
Drum Kit/Percussion
A more complete list can be found on the relevant Wikipedia page.