Full Band – refers to a complete set of instruments plus a vocalist or two — drums, bass guitar, electric guitar, keyboards, etc. They can generally play any song including those for party and dancing time.
Acoustic Band – refers to those with no drums, generally, a percussionist takes the place of the drums. Other instruments generally do not need the use of electricity as well, i.e. an acoustic guitar as opposed to an electric guitar.
Choir – refers to groups with several vocalists who specialize in blending their voices, usually they have a keyboardist or a guitarist with them, although some groups also sing acapella (without instrumentalists)
String ensembles – refers to groups with string instruments (may include a violin, a cello, a viola, a double bass), a keyboard, and a vocalist or two.