al-Ākhirah (, derived from Akhir which means last, ultimate, end or close) is an Arabic term for "the Hereafter".
In Islamic eschatology, on the Day of Last Judgment, the natural or temporal world (dunya) will come to an end, the dead will be resurrected from their graves, and God will pronounce judgment on their deeds, consigning them for eternity to either the delights of jannah (paradise) or the flames of hellfire of jahannam.
The belief that death is not the end of existence, but a transferral from the temporal world to the everlasting world, (al-Ākhirah), is a belief Islam shares with other Abrahamic religions such as Judaism and Christianity.
Al-Ākhirah is referenced dozens of times in the Quran in numerous surahs where among other things, believers are told it makes "the enjoyment of this worldly life" (dunya) appear "insignificant" (Q.9:38).
In connection with the Last Judgment, it is traditionally considered to be one of the six essential beliefs of Muslims, (along with Tawhid (monotheism), angels, the four Revealed Books (Injeel, Taurait, Quran and Zabur), prophets and messengers, and predestination). In Islamic doctrine, Al-Akhirah is necessary because the pious often suffer and unbelievers often prosper and enjoy themselves in the temporal world. To rectify that and to bring justice, Al-Akhirah with rewards of Jannah and punishment of Jahannam is necessary.
Importance
In the Quran, dunya is contrasted with akhira as "now" v. "later" and also as something negative v. something positive.
The Quran acknowledges the "necessity" of dunya for "carrying out the divine will", where duties should not be neglected, saying: "Ordain for us the good in this world [al-dunya] and in the hereafter [al-akhira]" (Q.7:156); and Muslim intellectuals (such as Muhammad Darwazah) have emphasized the importance of dunya in Islam: "'Islam is a religion of the world (din al-dunya), of government, society, moral order, to the same extent as it is a religion of faith and belief and the next world (din al-akhirah).'"
But the "usual contrast" between the two realms is as "two clear moral alternatives" that the individual has to choose between as "the focal point of his or her attention and activity" "Whosoever desires the harvest of the akhira, We will increase for him this harvest. And whoever desires the harvest of the dunya, We will give it to him, but he will have no share in the hereafter" (Q.42:20); "Life in the dunya is nothing but a distraction and a sport, but in the dār al-akhira is life, if only they knew" (Q.29:64). On the other hand, some Muslim mystics assert the two realms are "in a constant state of interpenetration", (according to one Todd Lawson), as expressed in the hadith: “the Garden is closer to you than the strap of your sandal and so is the Fire”.
Pre-dunya
The Quran makes "no mention of the pre-existence" of human souls before birth aside from "the rather ambiguous reference" in one verse: "When your Lord took from Banī Ādam [the human race] their progeny from their loins and made them testify concerning themselves, 'Am I not your Lord?' They replied, 'Yes! we do testify. That you may not say on the day of resurrection, truly we were ignorant of this.' (Q.7:172) This verse was traditionally interpreted to "affirm the idea of pre-existence", though in modern times it is thought to refer to humanity's responsibility to "the primordial covenant" man made with God.
Barzakh
In Islam, Barzakh is a state that is neither part of the temporal world of dunya, nor the hereafter. It lies between them (Barzakh meaning "separation" or "barrier"). Specifically in Islam it refers to phase/stage after a person dies and before they are resurrected for Judgement Day. This is based on the verse:"... behind them is a barrier until the Day they are resurrected." Al Quran [23:100]
During this time many if not all Muslims believe the dead person will be given a taste of either the rewards or the punishments they will live with after Judgement Day.
Some scholars give a different definition of Barzakh: According to Ghazali, Barzakh may also be the place for those, who go neither to hell nor to heaven. According to Ibn Hazm, Barzakh is also the place for the unborn souls, existing in the lowest heaven, where an angel blows the soul into wombs.
End of the World
Muslims believe that preceding this Day will be "signs" or portents of the Hour or the signs of the Day of Resurrection, and they are divided into minor signs and major signs.