Giacomo della Porta's most famous church is probably the "Chiesa del Gesù" (lit. Church of the Gesu) in Rome. He also participated in St. Peter's Basilica in Vatican (if I'm not mistaken, he worked...
A 'church' may have been created to keep track of members within that religion, to recruit more followers and track the loyalties of members within the proximal areas of the church. Churches are...