Every society has had its own mythology and explanation for how our world was created and why thinks work the way they do. Norse mythology is no different. In the beginning there were Muspelheim and Niflheim, fire and ice. Over time the fire began to melt the ice and a mist was formed, Ginnungagap, in this mist the first two beings are formed. First was Ymir, a frost giant of incomprehensible size, then the cow Audhumbla was formed. Ymir survived off Audhumbla's milk and one day has he slept his sweat fromed into the first two giants or jötnar as the Norse called them. Búri fathered Borr who then fathered three sons named Odin, Vili, and Vé who would become the first of the race known as the Aesir. One day the three brothers decided they could make more out of the world than what there currently was and decided to kill Ymir and used his body to shape the world. The brothers shaped his flesh into earth, blood into seas, bones into mountains, teeth fragments into stones, hair into trees, skull into sky as the sun, brains into clouds, and eyebrows into Midgard's walls.

Asgard

Asgard is the home of the Aesir, the first race of gods. It is said to be full of Viking mead halls and revelry, and nowhere more so than Valhalla. Valhalla is Odin's mead hall and if the home of all those who fall in noble combat, warriors to the end. They are selected by Odin's handmaidens, the Valkyries, and will join the Asgardians in final battle at Ragnarök.

Vanaheim

Vanaheim is the home of the Vanir and their magic. After the war of the gods it is left mostly empty with a majority of the known Vanir relocating to Asgard after the war in the name of peace. Even without it's major deity's it is still the home of the strange magic known as Seidr. Most never bothered to learn Seidr as it was focused on trickery and miss-direction as well as growth and fertility and was considered a shameful magic as it was focused largely on deception, though master knew it could grant them glimpses into the future.

Alfheim

Alfheim is the home of the Elves (or Light Elves). This world is unusual as it has no night, the sun lowers down and then travels along the horizon until it comes up again in the East leading to several hours of twilight but no true darkness. Little else is known of this world aside from being the home of the elves, but we do know that the elves all swear fealty to Fray and that they are talented users of Alf Seidr, their modified version of the Vanir's Seidr.

Midgard

Midgard is the home of the Humans. Midgard is simply portrayed as the world we live in, protected by Odin and his brothers with Ymir's eyebrows. Little is explicitly stated about Midgard so it has been widely interpreted. Midgard is know to be encircled by Jörmungand the Midgard Serpent who will fight Thor at Ragnarök.

Svartalfheim

Svartalfheim or Nidavellir is the home of the Dwarves or Dark Elves. The name and title for this species differs between the eddas. Originally called the Dvergar (translated to dwarves) in the Poetic Edda, Snorri changes the name to Svartálfr (translated to dark elf) in the Prose Edda. Snorri's label is also where we get the more broadly used name of Svartalfheim, sometimes called Dark Alfheim. Portrayed as a large underground cavern Svartalfheim was created when maggots that would eventually evolve into dwarves ate out large spaces in Ymir's flesh. The dwarves are known for their superb fording and crafting of Thor's hammer.

Jotunheim

Jotunheim is the home of the Giants. Aside from Asgard, Jotunheim is where most stories from Norse Mythology take place. Home to beings that use magic as often as they blink and breath Jotunheim is a strange and wonderous place. Though its inhabitants natural forms are colossal many giants will scale their surroundings down to more easily interact with other beings.

Niflheim

Niflheim is a land without any natural inhabitants other than the cold and snow. There are three core groups or beings that reside here. First there are several frost giants who chose to live here as it gives them a greater access to their magic but many who chose this route are more solitary beings. Next we have some of the dead. We already know that most noble dead end up in Valhalla; however, most end up in Helheim, those are the normal people who die of common causes. But Hel wont accept all souls. Souls that are deemed to be too wicked will end up roaming through Niflheim is perpetual cold and suffering until Ragnarök. The final creature is Nidhogg the dread corpse eater. Nidhogg is a large dragon who wants to see the tree destroyed because he hates the eagle Hraesvelgr who sits at the top, and as such spends most of hit time biting at the roots of Yggdrasil trying to kill the tree. Nidhogg survives by consuming the souls of those so wicked they were barred from Helheim.

Muspelheim

Muspelheim is the home of the Fire Giants and their lord Surtr. As Niflheim is the home of cold and snow Muspel is the home of fire and heat. We know very little of Muspel other than its residence and elemental contents, but we do know that is residence will have a great effect on Ragnarök when they will storm out on the side of Loki to fight the gods, and their ruler Surtr will take Fray's sward and kill him with it.

Helheim

Helheim (or Hel) is the home of the dishonorable dead. All those who die and aren't chosen for Valhalla or Fólkvangr end up here. Some souls may be deemed too wicked and will be locked out of Helheim's gate and forced to wander Niflheim forever. Helheim is ruled by Hel, she is the daughter of Loki and a giant. She chose to reside among the dead upon Odin's offer as they were more accepting of her as her body was living on one side and a corpse on the other. 

The Tree

Just as with all the worlds there are many creatures who live in Yggdrasil's branches. Two of the most important are Ratatoskr the squirl and Hraesvelgr the eagle. Hraesvelgr serves a similar role to Nidhogg and try's to destroy the world tree from the top because he wants Nidhogg to die. Ratatoskr encourages the both of them by running up and down the branches ferrying the twos insults to each other.

The Roots

The most notable difference between the two eddas is the location of the three roots of Yggdrasil. Even though the Poetic Edda comes earlier most scholars follow Snorri's version  in the Prose Edda as it is more specific and fits better into the worlds. Both agree that one of the roots resides in Jotunheim. Snorri tells us that this root is in the well of wisdom, Mimisbrunnr, guarded by the giant Mimir. The Poetic Edda places the other two in Midgard and Hel without a specific location. According to Snorri the second root is in Asgard. It the well of prophecy, Urdarbrunnr, and is guarded by the Norns. The final well, he says, is in Niflheim and is the well of chaos or life force, Hvergelmir, it is guarded by Nidhogg. 

Aesir

Odin

Odin is known as the All-Father among his other titles for being the first God. He is known for his wisdom and battle strategy. In his search for all wisdom he as both lost an eye and hung himself from Yggdrasil's branches with a spear in his side for nine days. Odin is the father of several gods (he gets around) and the husband of Frigg.

Frigg

Little is known of Frigg, but she is Odin's wife and the mother of Baldr and Hodd.

Thor

Thor is the son of Odin and the husband to Sif. He is know for wielding his hammer, Mjolnir, against the giants and for being fond of humans.

Sif

We don't know a lot about Sif but she is Thor's wife and known for her beautiful hair.

Baldr

Baldr is the husband of Nanna and twin brother of Hodd. Baldr is know for being the most beautiful and loved of all the gods. When Hodd killed him every being and thing wept for his death.

Hodd

 All we know about hodd is that he was the blind twin of Baldr and was tricked by Loki into killing Baldr.

Vidar

Vidar is Odin's son and the god of shoes, he avenges Odin at Ragnarök by killing Fenrir the Wolf.

Tyr

Tyr is Odin's son and the god of courage. When the gods managed to first bind Fenrir Tyr sacrificed his hand to trick the wolf.

Heimdall

Heimdall guards the Bifrost (the bridge to the other worlds). He was born of Nine mothers and is charged with waking all the sleeping gods for Ragnarök.

Bragi

Bragi is Odin's son and the god of poetry and the husband of Idunn.

Idunn

Idunn is Bragi's wife and keeps the apples of youth.

Vanir

Njord

Njord is the god of the sea. He is the father of the twins Frey and Freya and the husband of the giant Skadi. Njord is known for his imaculate feet, smoothed from years of standing on the beach as the tide flows.

Frey

Frey is the son of Njord and brother to Freya. He is the god of summer and lord of Alfheim. Frey gives his sward, Sumarbrant, to his servant Skírnir so Skírnir will carry his marriage proposal to the giant Gerd. This decision will lead to his death at Ragnarök at the hands of Surtr weilding Fray's own sward.

Freya

Freya is the daughter of Njord and twin sister to Frey. She is married to the missing god Odr. Her tears turn into the finest gold.