The Vaishnava understanding, based on Bhagavad-gita and other Vedic literatures, is that there is one Supreme Personality of Godhead, Bhagavan, who is the source of everything else. There are representatives of the Lord called demigods or devas, who are like directors and officers in the government of the Supreme Lord. They are in charge of administration of universal affairs. Although very, very powerful and exalted in their position, it would be very wrong to consider these demigods to be on an equal level with the Supreme Lord, as much as mistaking a minister or ambassador of state to be the king.
HH Romapada Swami
Why so many Gods in Hinduism