A myth is a story or series of stories used to explain the world around you and describe what is happening, such as why weather happens. Myths usually have heroes, gods, and creatures that are bigger or more fantastic than real life, or sometimes just normal people doing amazing things.
Some myths try to explain the natural world. One example is the Greek myth of Arachne. She believed that she could weave far better than anyone else, including the goddess Athena. So, Athena challenged Arachne to a weaving contest. Arachne lost, then was turned into a spider. This myth explains why spiders weave webs.