A god is a higher being that stands above nature. It has powers and properties that cannot be explained in a natural way. Many people believe in such beings, but they often have very different opinions about what a god is. It is also not always clear what is a god, what is a spirit and what is a demon.
For some religions, there is only one God. This God can do everything and knows everything, and he created the world. Judaism, Christianity and Islam believe in such a God. The belief in one God is called monotheism.
Other people believe that there are several gods and goddesses. Often these gods and goddesses are siblings or parents and children of each other. They have different tasks. For example, among the ancient Romans, Jupiter was the father of the gods, the god of the sky who provided thunder and lightning. Venus was the goddess of love and Mercury was the messenger of the gods who brought news from the gods to the people.
The belief in many gods is called polytheism. The Germanic tribes and the ancient Greeks were also polytheists, and even today in India the Hindus believe in many gods. Some scientists say, however, that even if a religion has many gods, it may ultimately always be the same God, but in different roles.