When applied to religion or philosophy, it is the idea that many, or even all, beliefs, are equally valid. Pluralism denies that there is one absolute principle or truth behind the universe. With regard to God, pluralism says that no one religion can exclusively claim to know the truth about God. The beliefs of a buddhist, a hindu, a muslim, a Roman Catholic, or a Sikh, are all equally valid and true. The emphasis is on the sincerity of the believer, rather than on what he or she actually believes.
Pluralism is very tolerant.
It tolerates all kind of beliefs, even though they may contradict one another. There is only one kind of belief that it will not tolerate, and that is, the belief that doesn't tolerate other beliefs. You can believe whatever you like, except you must not believe that others are wrong in their belief. Pluralism goes hand in hand with relativism. Relativism is the idea that all things are relative.