Folkvangr

Fólkvangr appears in two medieval texts, and they say almost the same thing. In the Eddic poem Grímnismál, Odin, disguised as Grímnir, lists the dwellings of the gods, and Fólkvangr is the ninth. There, stanza 14 says, Freyja decides the choice of seats in the hall; half the slain she chooses every day, and Odin has the other half. Snorri Sturluson retells this in Gylfaginning 24, written around 1220: Freyja, the most renowned of the goddesses, has the dwelling in heaven called Fólkvangr, and wherever she rides to battle, half of the slain are hers and half are Odin's. He then quotes the same stanza, with a slightly different first line.
Snorri adds the name of her hall, Sessrúmnir, and says only that it is large and fair. In Skáldskaparmál, where he lists the ways a poet may refer to Freyja, she is 'owner of the slain and of Sessrúmnir and of tomcats'. The name seems to mean something like 'roomy in seats', which suits a hall where Freyja allots the seating. The word also turns up among the names for ships in the þulur, the verse lists of names copied with Snorri's Edda, so it was not used only for her hall.
That is the whole of the mythological evidence. No source describes the field itself, says what the dead do there, or says whether they fight beside the gods at Ragnarök. Neither text even states outright that Freyja's half of the slain lives in Fólkvangr, though the seating in the hall implies it. Valhalla, by contrast, gets pages. Grímnismál 23 gives it more than five hundred doors, with eight hundred einherjar marching out of each, and Snorri describes the boar Sæhrímnir, cooked every day and whole again by evening, and the einherjar fighting one another in the yard each day before they sit down to drink (Gylfaginning 38 and 41). Snorri also leaves his own accounts unreconciled: in Gylfaginning 20 he says that all who fall in battle are Odin's adopted sons, and that Odin gives them Valhalla and Vingólf. Modern pictures of Fólkvangr as a second Valhalla, full of warriors training for the last battle, borrow those details. The sources never give them to Freyja's field.
The only other hint comes from a saga. In Egils saga, ch. 78, Egill Skalla-Grímsson's son Böðvarr drowns, and Egill shuts himself in his bed-closet to starve. His daughter Þorgerðr rides to him and announces that she has had no supper and will have none until she has it with Freyja. The saga never says so outright, but the scene reads as a ruse to keep him alive: she chews dulse, which makes them both thirsty, the drink turns out to be milk, and she talks him into composing a memorial poem for his son, which becomes Sonatorrek. Her line shows that a saga writer in 13th-century Iceland could have a woman speak of death as going to Freyja. It does not name Fólkvangr, and one sentence is not a description of an afterlife.