Concert choir is a group of choir members performing to a huge amount of audiences. Usually a "middle" level choir class, but some schools offer it as "advanced" level. Almost always plays with accompanist and includes different moods depending on the piece.
Standing straight is required for those serious songs, but joyful pieces require you to move around a bit or even clap your hands.
Concert choir has the most members than other groups.
I am in Concert Choir, but today, I am also in Chamber Singers.