The first god to come into existence was Chaos, whose name means ‘a chasm/empty space’. After him came Earth, Tartarus (the underworld) and Love.
Earth produced some children by herself: Sky and Sea. With Sky she then had many children, including the Cyclopes, and the Nymphs, and the Titans.
Two of the Titans, Kronon and Rhea, had children including Zeus and Hera, who became the king and queen of the gods.
As the generations went on, the gods had more and more children. Each of these was responsible for a different part of the universe. The earlier gods were responsible for large places, and the later gods were responsible for smaller places or for types of activity. For example, Apollo is responsible for music.
So, through this family of the gods, all of the parts of the world came into being.