Greek mythology are all the myths told by the Ancient Greeks. Mainly present in Greece, this mythology was exported to Egypt and Asia Minor in the 4th century BC, after the conquest of Alexander the Great.
Most of this myth knowledge comes from Hesiod's Theogony which traces the origins and genealogies of numerous Greek deities.
Contrary to the Norse mythology, Greek mythology is more focused on heroes getting the help (or harm) from the deities.