The Aesir were the primary race of gods, which included Odin, Thor, Tyr, Balder, and Heimdall, among others. They lived in Asgard and held temporary power over the cosmos. Aging like mortals, these gods renewed their youth by eating magic apples. Their reign would end and they would die at Ragnarok, when evil overcomes good in a final battle.
The Vanir were a secondary race of gods, not essentially different from the Aesir. In ancient times the Vanir and the Aesir battled one another until a compromise was reached in which the Vanir were admitted into Asgard. Among these gods were Frey and his beautiful sister Freya.
The Giants, whether Frost-Giants or Mountain-Giants, were terrible magicians who lived at Jötunheim, engaged in contests with the gods, and would shatter the cosmos at Ragnarok.
The Dwarves were a subterranean race of craftsmen.
The Valkyries, "choosers of the slain," were female warriors who selected brave mortal fighters who died in battle to live in Valhalla in Asgard. Attendants of Odin, the Valkyries were also immortal waitresses that refilled the drinking cups in Valhalla. They were visible only to men about to die fighting.
