As with most of the nine worlds, Alfheimr is the main home of a specific race of beings. That race, is the Light Elves. Alfheimr is quite an important place to the overall concept of Norse Mythology.
There is extremely little known about Alfheimr. As many of you know, there are nine worlds in the Norse Mythos, separated into three tiers.
"Alfheim (Old Norse: Ālfheimr, "elf home") is one of the Nine Worlds and home of the Light Elves in Norse mythology and appears also in Anglo-Scottish ballads under the form Elfhame (Elphame, Elfame) as a fairyland, sometimes modernized as Elfland (Elfinland, Elvenland)." (1)
Frey, twin brother to Frejya, the god of life, fertility, rain, the harvest, etc. is said to find his home in Alfheimr. The lord of the Elves, as some call him.
In the "The 20th-century fantasy writer J. R. R. Tolkien anglicized Álfheim as Elvenhome, or Eldamar in the speech of the Elves. In his stories, Eldamar lies in a coastal region of the Undying Lands in the Uttermost West. The High King of the Elves in the West was Ingwë, an echo of the name Yngvi often found as a name for Frey, whose abode was in Álfheim according to the Grímnismál." (1)