Polytheism

Polytheism is belief in and/or worship of multiple gods or of multiple gods and goddesses.

Confusion
Some religions could be considered polytheism in disguise, like Catholicism. The Catholic encyclopedia states: "In the unity of the Godhead there are three Persons, the Father, the Son and the Holy Spirit, these three persons being truly distinct from one another. Thus in the words of the Athanisian Creed: 'the Father is God, the Son is God and the Holy spirit is God'."

It however, then goes on to say that this does not mean there are three Gods, and does not bother to explain this.

Also, religions like Hinduism are actually examples of monotheism since there is only one god. Lord Brahma the creator; Lord Shiva the destroyer, Goddess Laxmi, Lord Ganesh and all the hundreds of others are all just different incarnation of the one god.

Monotheism and polytheism
Christians like to see themselves as monotheists though as stated above it is not clear that they are. Westerners also like to claim that monotheism is in some unclear way a higher form of religion than polytheism. Alternatively it appears to be a historical accident that the Abrahamic religions, Christianity and Islam, came to dominate in the West. The Japanese are technically advanced and Japanese Shinto belief is polytheistic (although most Japanese today are Buddhist as well as Shintos).