An orchestra is a large group of musicians who play classical music, while musicians who form a band are generally fewer in number and usually play popular music.
An orchestra made up of about 50 musicians or fewer is called a "chamber orchestra." A "symphony orchestra" or "philharmonic orchestra" can be composed of approximately 100 musicians. An orchestra is composed of percussion, string, woodwind and brass instrumentalists. It is usually directed by a conductor. A band generally plays pop, rock or jazz music with a larger variety of instruments. The word "orchestra" has Latin and Greek origins, and the original definition was a specific area in a theater. The word "band" comes from Middle French originally and meant "organized group."