No, choir in a church is not the same thing as an a cappella group.
While both involve vocal harmony, a choir in a church and an a cappella group differ in purpose, style, and setting. A church choir is one that do performs sacred music during religious ceremonies, often accompanied by instruments. It involves singers of various vocal ranges, following a conductor.
So, one need to know that an a cappella group performs without instrumental accompaniment, focusing solely on vocal harmonies. A cappella groups often explore a diverse range of genres, including popular and secular music, and may perform in various settings beyond religious contexts.