Short answers, pulled from the story.
Njörðr is a god among the Vanir who rules over the movement of winds and has the ability to calm both sea and fire. He originates from Vanaheimr and is devoid of Aesir stock before being traded as a hostage to the gods.
Odin appointed Njörðr and Freyr as priests of sacrificial offerings during the peace agreement between the Aesir and Vanir after their war ended. This event occurred when the two sides became tired of fighting and exchanged hostages including Mímir and Kvasir.
Gylfaginning describes Njörðr as living in the heavens at Nóatún which was given to him by Odin as his temple dwelling place. The text states he also rules over the movement of winds while residing there.
Njörðr's wife is Skaði who is the daughter of the jötunn Þjazi following an agreement where they would spend nine nights in Þrymheimr and three nights in Nóatún. They ultimately separated because Njörðr hated the howling of wolves in the mountains and Skaði could not sleep on sea beds due to the screeching gulls.
Chapter 24 of Gylfaginning describes Njörðr as the father of two beautiful and powerful children named Freyr and Freyja. Lokasenna confirms that Freyr was produced with his unnamed sister whom some theories identify as Nerthus or a divine pair.