Ilúvatar made divine music with his creations, the Ainur. Melkor, one of the greatest of the Ainur, in his pride broke the harmony. Ilúvatar then began the music once more, in which Manwë, Melkor's brother, sang the leading part. Yet again, the harmony was broken.
Finally, Ilúvatar began a third theme which the Ainur could not comprehend since they were not the source of it. He then ceased the music and showed to the Ainur the essence of what their song symbolized, the history of a whole world. This is known as the "Vision of Ilúvatar". The Ainur became fascinated by it, and asked Ilúvatar to put it into being.
Ilúvatar spoke "Eä", that is, "Be!". This command created the universe, and therefore the universe became known as "Eä". Four of the Ainur who possessed the greatest power formed a region within Eä which they called Arda, the world we all live.