教会 is like organization,we always say that "XX教会“ means one community or organization 教堂 is The church,is building

教会：A religious organization 教堂：A church, an actual building.

教会是基督教各教派的信徒组织，教堂基督教进行宗教仪式的建筑物,有多种风格,如哥特式、拜占庭式的，象这种词查词典就可以了。

教会 is the Church. 教堂 is a church.

ITs interesting that in English church may be either 教会 or 教堂, but in Chinese 教堂is never 教会。