THE CREATION OF ARDA
Ilúvatar and the Ainur
In Tolkien mythology, the One God is known as Ilúvatar. His first creation was the Ainur, who were the offspring of his thought. They were created in the depths of time, even before the creation of the world. The Ainur were primordial spirits, and the eldest and mightiest of Ilúvatar's creations. Because they were created from Ilúvatar's thoughts, each Ainur only had an understanding of the part of his mind that he or she came from.
The word Arda signifies the world, and all that is in it. Arda was created through the Music of the Ainur, but it was ultimately Ilúvatar who gave Arda true form. Once Arda had been created, many of the Ainur descended into it (taking material form) to guide its growth.
The Valar, the Maiar, & Melkor
From there, the Ainur split into two groups. 14 of them were more powerful, and they became the Valar (the Powers of Arda). The rest of the descended Ainur became a lesser order know as the Maiar.
There was one exceptional Ainur. He was Melkor, and he understood all parts of Ilúvatar's thoughts, and not just the one thought that gave birth to him. When the Ainur went into Arda, Melkor did not become one of the Valar, but became the first Dark Lord.
The Valar and Maiar prepared Arda to be the dwelling place of the Children of Ilúvatar, who were the Elves and Men. However, long before the Elves and Men came to Arda, Melkor and the Valar and Maiar fought over the fate of Arda. Eventually the Valar completed the shaping of Arda, but Melkor had, in some way, marred every part of the world.
The Spring of Arda
Before the awakening of either Elves or Men, the Valar settled on the green island of Almaren. This was the time called the Spring of Arda, when the world was lit by the two Lamps of the Valar. Almaren lay in the centre of the world, where the light from the two lamps mingled. Almaren was the site of the first defeat of the Valar at the hands of Melkor. Almaren was destroyed, both of the Lamps of the Valar were thrown down and the Valar left Middle Earth. They then founded Valinor, the Undying Lands, in Aman.
The Years of the Trees
The Years of the Trees were the long ages between the founding of Valinor and its eventual Darkening. It was during this time that the first Elves awakened. Also during this time, the Two Trees lighted Valinor, and Middle Earth was lit by starlight alone. Melkor and his evil ally, Ungoliant (possibly an evil spirit, she took spider form) destroyed the Two Trees, but not before their last flower and fruit were made into the Sun and Moon to light Middle Earth. This signifies the beginning of the first age.