In Norse mythology, Fólkvangr, (meaning "field of the host", "people-field" or "army-field"), is a meadow or field ruled over by the goddess Freyja. It is the place where half of those that die in combat go upon death, while the other half go to the hall of the slain, Valhalla, ruled over by the god Odin. Not only soldiers have gone to Fólkvangr, rouge Vikings who killed others were brought to Fólkvangr even if they were not soldiers, however only soldiers have gone to Valhalla to become Einherjar.
When Magnus and his friends go here, Magnus describes it as a party. Unlike Valhalla where fighting is encouraged, Magnus notes that swords and shields are strewn about on the grass. People are sunbathing and playing sports. It's warm and vibrant and a stark contrast to Valhalla.