If you think of religion, monotheism is the most popular view. Polytheism is the second most popular. However, they're not the same. Each religion has its advantages and disadvantages. One of the most important differences is the way that each religion views the world. Monotheism can be peaceful and allow everyone to worship the one God. This helps to prevent conflicts between different civilizations.
Mythology
The main difference between monotheistic or polytheistic mythologies lies not in the nature of gods but in how they are presented. In polytheistic mythology the gods are seen as the results of long-term interactions among gods.
There were twelve Olympian Gods in ancient Greece. Other gods were Demeter, Apollo, and Artemis. Each god served a specific purpose, including providing sustenance. Exceptions were made, however, like Hades, who lived underworld.
Morality
There are many differences between monotheistic society and polytheistic society in terms of their moral views. Monotheism favors absolute values while polytheism allows you to have relative morality. The two approaches are very different, though both tend to stress the importance of individual responsibility.
Monotheistic systems generally elevate one god to a supreme position. They then treat the other gods as manifestations of this supreme god. They then become essentially monotheistic.
Religion
Two different religions are monotheism and multitheism. Monotheists believe there is a single divine creator. The Polytheists on the other side believe in multiple deities. While each approach claims to be right, both sides disagree on what makes a religion true.
Polytheism was the source of monotheism. However, it is not clear why. One of two factors have been suggested by modern religion philosophers as the reason for monotheism's rise.