The Norse Gods and Goddesses
The Æsir are the decedents of the god Búri, the god spawned from the ice when fire and ice clashed in Ginnungagap (empty void.) Búri and his kin lived alongside the early races of giants. Búri had a son called Borr, and Borr had three sons.
These sons were Odin, Vili, and Vé. They went on to start a war with the giants that ended with the creation of the realms of Jötunheimr, Miðgarðr, Ásgarðr, and Svartálfaheimr. Múspellsheimr, Niflheim, Vanaheimr, Helheim, and Ljossálfaheimr seem to be in existence before the coming of the Æsir.
The Vanir consist of Freyr, Freyja, Njörðr, and a few briefly mentioned deities of the Vanir tribe. These gods are more akin to fertility, magic, sex, harvest, and overall primal/nature gods, while the Æsir usually concern themselves with things like war, poetry, law, love, strength, etc.
The Vanir are more centered around nature and the harvest. They are not much different than the Æsir other than that regard. In fact, they had a great war but exchanged hostages and now they've interbred and coexist to the point that they are hard to tell apart sometimes.