Wind instruments are all instruments whose sound is generated through a column of air produced by an instrumentalist, an air pocket (as on bagpipes) or through a mechanical wind tunnel (as on the accordion). The term wind instruments is used because more poetic than air instruments.
Wind instruments are classified in 2 categories
The woods: are characterized by the system of sound emission. It can be produced using a bevel (the tip on the flutes), either by the vibration of a simple reed (clarinet principle) or the vibration of a double reed (as for the oboe). The instruments can be made of metal (such as saxophone), crystal (for flutes), ceramic (for ocarina) or plastic (recorders).
The brass: as for them gather the wind instruments whose sound is produced by vibration of the lips in a mouth. The common point of these instruments is not the materials in which they are made, but the way they produce sound. For example, we can find the trumpet (which is metal), the book horn (which is wood) or olifant (which is ivory).