The Norns are three female divine beings who have more influence over the course of destiny than any other beings in the cosmos. They dwell within the Well of Urd beneath Yggdrasil, the great ash tree that stands at the center of the universe and holds the Nine Worlds in its branches and roots. They shape destiny by carving runes into the trunk of the tree, or, in some sagas and poems, by weaving destiny like a web or tapestry.
Their names are Urd (Old Norse Urðr, “What Once Was”), Verdandi (Old Norse Verðandi, “What Is Coming into Being”) and Skuld (Old Norse Skuld, “What Shall Be”). via - http://norse-mythology.org/