1) This passage describes the early history of the Elves in Valinor, a time referred to as the "golden age". It introduces Finwe, Miriel, and their son Feanor.
2) Miriel grew tired after giving birth to Feanor and fell into a deep sleep, eventually dying. Finwe later remarried to Indis and had two more sons, which angered Feanor.
3) Melkor, who had been pardoned by Manwe but lost his place of power, began spreading lies and distrust among the Elves, particularly targeting Feanor. He sought to turn Feanor against the Valar.