The ancient Greeks believed in several gods. One god had several tasks. Anyone who needed something prayed to this god or visited a temple.
The most important god was called Zeus. Besides him, there were brothers, such as Poseidon, the god of the sea. Zeus also had several children, like Aphrodite, the goddess of love. Some gods had children with humans, who were then demigods. It was believed that the twelve most important gods lived on the highest mountain in Greece, Mount Olympus.
Among the Greeks, the gods also appear in sagas and other stories. In Homer's stories about Troy, for example, gods help the heroes. For many Greeks, the gods were very important, others hardly believed in them at all. Philosophers like Socrates did not speak so much about individual gods, but about the "divine". This is somewhat reminiscent of the single God in other religions.
In ancient times, peoples had their own gods. But it was seen that gods from other peoples were similar to their own. Among the Roman gods, Zeus was called Jupiter, Aphrodite was called Venus.
Later, people in Europe were Christians. But even then there were artists who painted Greek gods or showed them in statues. The old stories still lent themselves well to magnificent paintings.