Roman mythology is a huge collection of stories, started in Ancient Rome, about the beginning of the world, and the lives and adventures the many Roman gods, goddesses, and heroes. Each god, each goddess had a cult to take care of their temples or other holy places.
The myths of the Ancient Romans are often called "Greco-Roman". Originally they were similar to the Greek mythology of the Ancient Greeks, and later the Romans added Greek stories for their Roman gods, so they became even more similar.
The gods and goddesses in these stories have lots of magic powers. They can make themselves invisible to humans and move to any place in a very short time. They can change people into animals or animals into people. They have no disease and can only be hurt by very unusual causes. This is called being immortal; they can never die.