Many believe in life after death because in the classical Jewish tradition there are teachings on life after death. (e.g. humans have a soul which will one day return to God, a future judgment when some will be rewarded and others punished.)
Mishnah contains recorded debates and judgements including issues of life after death
(Maimonides outlined Thirteen Principles of Faith for Jews, 13th speaking of a revival of the dead…when it shall please the Creator.)
Afterlife is dependent on how one lived during their time on Earth (good life = heaven, bad life = hell)
Sheol = after death Jews would descend to a dark place called Sheol (early belief)
Gan Eden and Gehenna = further teachings developed including teachings on Gan Eden and Gehenna.
Sheol became a place of purification, or waiting, before the individual was sent to either Gan Eden or destroyed completely.
OlamHa-Ba = Early Rabbis taught if lived according to Halakhah (scriptures w laws for living), you’d be rewarded in a world to come
Later teachings included the idea of judgment would happen after the coming of Mashiach (messiah)
Judaism teaches how the person lives is important and good deeds should be done for owns sake
There will be punishment or reward for the way they have lived, but there's no clear teachings on EXACT nature of heaven/hell
Resurrection = some believe the soul and body would reunite when the Messiah comes (resurrection of the body)
Some believe the soul would be eternal (immortality of the soul)