The Norse mythological texts record three primary places where the dead were perceived to go: Helheim (Old Norse Helheimr, “the home of the goddess Hel“), Valhalla (Old Norse Valhöll, “the hall of the fallen”), and Folkvang (Old Norse Fólkvangr, “the field of the people” or “the field of warriors”).
But they're indistinguishable and don't have any major differences between them.
Valhalla is presided over by Odin, and to gain entrance to it, one must be chosen by him and his valkyries, the “choosers of the fallen.”
Similarily, entrance to Folkvang is dependent upon being selected by Freya.
Valhalla is often depicted as a realm where distinguished warriors engage in a continuous battle, and just such a place is described, in important early sources, as being located beneath the ground – and, intriguingly, without the name “Valhalla” or a cognate anywhere in the account.
source: Ellis, Hilda Roderick. 1968. The Road to Hel: A Study of the Conception of the Dead in Old Norse Literature. p. 85-86.
- Folkvang is the ninth, and there Freyia arranges
the choice of seats in the hall;
half the slain she chooses every day,
and half Odin owns.
source: 1996 Carolyne Larrington in The Poetic Edda “Grimnir’s Sayings”
The only difference that is pointed out, is in the way that the dead are chosen to stay. Odin chooses for Valhalla, while Freya chooses for Folkvang.
Coming to the second part of the question:
And why did the need to have many "paradises" (whatever you many call it) exist?
Hel is a place where all humans have to go after their death:
“For there is a time
when every man
shall journey hence to Hel."
So before the dead finally reach Hel, Odin and Freyja select the ones who are worthy of living in Valhalla and Folkvang.
- Valhalla receives distinguished warriors.
- Folkvangr receives the rest of the warriors.
- Hel receives the rest of the dead.