Polytheism is a religious system that consists in the belief in different deities.
In polytheistic societies, the existence of multiple gods, usually each dedicated to a particular characteristic of nature, such as: thunder god, sun god, rain goddess, earth goddess and etc.
Polytheism was quite common in ancient societies, as in Ancient Greece, Ancient Rome and Ancient Egypt, for example. Currently, it is still present in some religions of African and Asian origin.
Each deity, in the polytheistic system, had special forces and powers, being specialists in certain areas, such as elements of nature, human relationships, objects, activities, and so on. For example, the ancient Greeks believed that aphrodite she was the goddess of love, beauty and sexuality; while Athena she was supposed to be the goddess of wisdom and civilization, and so on.
A particular feature of most gods in polytheistic societies was the presence of their unique personalities. The Greek and Roman gods, for example, according to their respective mythologies, lived directly interfering in the lives of mortals and, at times, acting cruelly.
Learn more about meaning of mythology.
Etymologically, the word polytheism originated from the joining of the Greek elements cops, which means "many", and theos, which means “god”, thus, the literal meaning of this term would be: “many gods”.
Polytheism and Monotheism
Unlike polytheism, monotheism consists of belief of only one god (or “God” in this case).
The main monotheistic religions are Christianity, Judaism and Islam.
Polytheistic deities could be represented under anthropomorphic forms (human figure and figure animal), while in monotheism "God" is usually described as similar to human beings, in appearance.
Learn more about the meaning of Monotheism it's from Theism.