The word hereafter means “last, next and last day” in Arabic.
Term Meaning: It is eternal life that will begin when the angel named Israfil blows the horn and heralds the end of the world. When the same angel blows the horn for the second time, people will be resurrected and brought to account. Then they will be punished and rewarded according to their faith and deeds in the world. Those in Heaven will enter Heaven, those in Hell will enter Hell and stay there.
Belief in the Hereafter is one of the fundamentals of belief. The word hereafter is mentioned in the Qur’an as “al-yevmü'lahir”, that is, “the day of judgment”, and it occurs after belief in Allah.
A person who does not believe in the Hereafter becomes a disbeliever because he denies the verses of the Qur’an.
(Catechism-I, Presidency of Religious Affairs)