Both sides were Christian churches but the Eastern one based around Byzantium was Orthodox while the Western one based around Rome and Pope was the Roman Catholic church. They still exist today except that the Orthodox church is not unified by a single leader and countries that practice Orthodox Christianity each have their own religious leader.
the world was bipolar, because the United states revolves around capitalism and the soviet union is revolves around communism... i dunno, that is the best answer i have without looking it up!
