What Are Creation Myths?

Creation myths are basically religious or spiritual explanations for the creation of the Universe, which are no longer widely held today.
Since man first began to think he has created belief systems which explain the world and its creation.
The Ancient Egyptians believed that at the dawn of time Ra, the Sun God, created the sky, air, moisture and the earth.  They also believed humans came from his tears.
In Norse tradition it was believed that the might God Odin (and his brothers) created the world from the killing of ice giants.   
In Aboriginal culture, people believed that the earth and people were created in Dreamtime - a time before time.  In Dreamtime, the elders woke up to wander the earth and transform plants and animals into human beings before going back to sleep.
The Aztecs believed Quetzalcoatl was the God of creation, learning and the winds.  
Many other creation myths have circulated and possibly will do so for as long as mankind exists.

I agree with Hedgehog, with one exception.  The myths don't have to be 'no longer widely held'.  The Genesis 6 day myth is still widely held by biblical literalists.