One of the Aratar, the eight greatest of the Valar, Aulë was the Vala concerned with the substance of Arda; rock and metal. As his name suggests, he was also the builder and inventor among the Valar. He constructed Angainor, the chain of Melkor, and the vessels of the Sun and Moon.
In anticipation of the coming of the Children of Ilúvatar, Elves and Men, Aulë went so far as to create a race of his own, the Dwarves. Ilúvatar granted them life, but would not suffer them to be born before the Elves, so Aulë set them to sleep in Middle-earth until the Elves had awoken.
When the Elves came to Valinor, the Noldor became fascinated by the lore of Aulë, and became his students. Fëanor was his greatest pupil, and from him learned the craft to make the Silmarils.