A religion that is based on a single God is considered monotheist and a religion that believed in a multiplicity of gods is known as polytheistic. Egyptian, Greek and Roman civilization are examples of polytheism. On the contrary, Christianity, Islam, or Judaism are monotheistic faiths.
General characteristics of polytheism
Anthropologists agree on the idea that the human being has a sense of transcendence, which means that man believes that there is something more than simple earthly life, and therefore believes that there is a higher entity that directs and governs the earthly life. If the superior entity is one we will talk of monotheism, but if there are several entities we are in the context of polytheism. The polytheistic civilizations understood that different natural phenomena correspond to some kind of supernatural force. Thus, if there were rays it is because there was a God who sent them and the same could happen with the clouds, storms, rain and all natural phenomena. Something similar happened with human passions, that they were understood as forces sent by gods who punished or advantages richly options men (Eros was the God of love and sexual desire for the Greeks, Thor was the God of Thunder in Norse mythology and Hepu was the God of fertility for the ancient Egyptians). Polytheism may be understood as a mindset, a way of understanding reality as a whole. Believing in many gods allows to explain the behavior of the nature and complexity of human relationships. In most visions polytheistic gods are described as if they were human and thus appear, for example, in the mythological accounts of the Greeks, in which the gods suffer, are annoyed, love and hate as if they were men and women of flesh and blood (this conception of the gods called anthropomorphism). Scholars of the religious phenomenon agree that polytheism had its apogee in the periods in which the society had a rigid hierarchical system. Polytheism did not disappear suddenly and proof of this is that the idea of a single God of Christianity was officially introduced in Roman civilization in the 4th century d. C. You must not think that Polytheism is a matter of the past, since nowadays Polytheism is still alive in Hinduism. However, it is not polytheism conventional, as there is a Creator God, Brahman, but this God presents manifestations or different deities (Vishnu, Shiva, Krishna, Cali or Ghanaian,) among other many deities.