On that Day, you will see the Faithful in such a condition that their Noor (Radiance/Light) will enlighten their front and their side. (A voice will be heard): Good tidings to you for you will get the eternal paradise beneath which rivers will flow. It is indeed a very big success of yours.
On that Day, the hypocrites will tell the Faithful: Just look at us also! We too may benefit from your radiance. They will be told: Return to the world and find out some other light. Then a wall will be raised between the said two groups. There will be a door in that wall. On one side of it will be only Mercy (for the Faithful) and on the other only punishment (for the deniers and hypocrites).
Fa Zu Re Ba…Azaab. (Surah Hadeed 57:13)
Translation: Then a wall will be raised between the Momineen and the Munafiqin (believers and show-makers). There will be a door in it the insider of which is Mercy and outside of it is chastisement.

One’s Noor Will Be Of No Use To Others
It is mentioned in commentaries that the Noor is front of believing men and believing women will be the light of their beliefs and love for and friendship with Aale Muhammad (a.s.). The Noor at their right will be the radiance of the prayers and worships. The Noor of some will be so bright that it will make things visible for eyes and that of some will be sometimes bright and sometimes dim. Such people will go on falling down and getting up and crying Rabbanaa Atmin Lana Noorana (8:66). Meaning: O Lord! Make our light full so that we may reach our destination.
Here one's noor will be of no avail to another. Though the hypocrites and the offenders will go on asking for the light of the lucky ones but it will be of no use. A wall will be erected between them and the faithful Momineen. According to tafseer, it is A'raaf.

Be Anxious About That Day’s Noor Only Today
Yunaa Doo Na Hum…Maseer (Surah Hadeed 57:14-15) meaning: The Munaafiqueen (hypocrites) will say: (O Faithfuls

Were we not with you? The faithful will reply: Indeed you were! But you desired way laid you and lengthy aspirations fooled you. You kept a distance from God and remained unmindful of this Day. Now there is no escape for you today. Your dwelling place is only Hell which is your shelter. What a bad shelter!
By the way, let there be some admonition also so that we may worry today about the light of that Day before the arrival of the moment when there will be no remedy or escape.

A’raaf, A Place Between Paradise And Hell
Third explanation of A'raaf is that it is a place (between paradise and hell where those people will dwell who were helpless such as minors, lunatics, children. Though they will not be as happy as those in paradise, they will be saved from the punishment of hell.
Hooraane bihishti raa dozakh buwad a'raaf az dozakhiyaan purs ke a'raaf bihisti ast
For the fairies of heaven, A'raaf is hell. But if you ask the people of hell, they will reply that A'raaf is paradise.