Why are they called brass instruments?
Brass instrument
A brass instrument is a musical instrument that produces sound by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips. Brass instruments are also called "labrosones", literally meaning "lip-vibrated instruments".
Baroque trumpet
The baroque trumpet is a musical instrument in the brass family. Invented in the mid-20th century, it is based on the natural trumpet of the 16th to 18th centuries, but designed to allow modern performers to imitate the earlier instrument when playing music of that time. Often synonymous with 'natural trumpet', the term 'baroque trumpet' is often used to differentiate an instrument which has added vent holes and other modern compromises, from an original or replica natural trumpet which does not.