Ive never been a part of a choir.
Ah, i suppose most people haven't been a part of a musical ensemble of singers. 
yea they are popular at churches
That's true, Churches are the most frequently associated group with a choir, alongside theaters and concert halls. 
oh yea? thats interesting.
secondary definition of a subset of an ensemble; thus one speaks of the "woodwind choir" of an orchestra, or different "choirs" of voices or instruments in a polychoral composition. In typical 18th- to 21st-century oratorios and masses, chorus or choir is usually understood to imply more than one singer per part, in contrast to the quartet of soloists also featured in these works.
Structure.
Choirs are often led by a conductor or choirmaster. Most often choirs consist of four sections intended to sing in
relay their vision to the singers. Choral conductors may also have to conduct instrumental ensembles such as orchestras if the choir is singing a piece for choir and orchestra. They may also attend to organizational matters, such as scheduling rehearsals, planning a concert season, hearing auditions, and promoting their ensemble in the media.
In worship services.
In worship services Accompaniment.
Most Eastern Orthodox Christian churches, some American Protestant groups, and traditional Jewish synagogues do not accompany their songs with musical instruments. In churches of the Western