You can hear the word fiberglass to describe a composite or correctly as the glass fiber reinforcing material of a composite material or as insulation.
Fiberglass is the fibrous form of any number of common glass compositions. The composition of the starting glass determines the physical properties of glass fiber.
It is not a composite but can be used as a reinforcing component of composite system such as epoxy/glass, polyester/glass, or vinyl ester/glass. The advertising term Fiberglass is often used to describe one of these systems such as the car has a fiberglass body or the boat is made from fiberglass.