The Nine Worlds

• ASGARD
• The abode of the Aesir and the Vanir after the two tribes were at peace.

• MIDGARD
• The abode of humans. It means middle earth or middle garden.

• VANAHEIM
• The abode of the Vanir before the peace.

• ALFHEIM
• The abode of the light elfs and their ruler, Frey.

• NIFLHEIM
• A region of cold. Hel's realm is here (in some sources).

• HEL
• The land of the dead. The way to this realm was through the land of the mountain giants. The connection between this and Niflheim is confusing. Hel is also the goddess of the underworld.

• JOTUNHEIM
• The abode of the Jotuns -- giants.

• MUSPELHEIM
• A region of fire. The fire giants -- sons of muspel -- live here, ruled by Surt.

• SVARTALFHEIM
• The abode of the dark elves -- dwarves. It is underground.

• NIDAVELLIR
• The abode of the dwarves. I don't see how this differs from Svartalfheim since the dwarves and the dark elves are one and the same.