Heaven as per Hinduism
From the viewpoint of Hinduism, heaven and hell are merely different worlds, bound by time, space, and causality. According to Hinduism, desires are responsible for a person’s embodiment. Some of these desires can best be fulfilled in a human body, and some in an animal or a celestial body. Accordingly, a soul assumes a body determined by its unfulfilled desires and the results of its past actions. An animal or a celestial body is for reaping the results of past karma, not for performing actions to acquire a new body. Performance of karma to effect any change of life is possible only in a human body, because only human beings do good or evil consciously. Human birth is therefore a great privilege, for in a human body alone can one attain the supreme goal of life. Thus, in search of eternal happiness and immortality, the apparent soul is born again and again in different bodies, only to discover in the end that immortality can never be attained through fulfillment of desires. The soul then practices discrimination between the real and the unreal, attains desirelessness, and finally realizes its immortal nature. Affirming this fact, the Katha Upanishad says: “When all the desires that dwell in the heart fall away, then the mortal becomes immortal and here attains Brahman.”
Hell as per Hinduism
Naraka is the Hindu equivalent of Hell, where sinners are tormented after death. It is also the abode of Yama, the god of Death. It is described as located in the south of the universe and beneath the earth.
The number and names of hells, as well as the type of sinners sent to a particular hell, varies from text to text; however, many scriptures describe 28 hells. After death, messengers of Yama called Yamadutas bring all beings to the court of Yama, where he weighs the virtues and the vices of the being and passes a judgement, sending the virtuous to Svarga (heaven) and the sinners to one of the hells. The stay in Svarga or Naraka is generally described as temporary. After the quantum of punishment is over, the souls are reborn as lower or higher beings as per their merits. In a few texts, a hell is described as a bottomless pit of darkness where souls are trapped for eternity and deprived of rebirth.
Salvation (or moksha) is reached when the worshiper is freed from the cycle of reincarnation, and his spirit becomes one with god. One becomes free by ridding oneself of bad karma—the effect of evil action or evil intent. This can be done in three different ways: through selfless devotion to and service of a particular god, through understanding the nature of the universe, or by mastering the actions needed to fully appease the gods.
In Hinduism, with over a million different gods, there are differences of opinion regarding the nature of salvation. The Advaita school teaches salvation occurs when one can strip away the false self and make the soul indistinguishable from that of god. The dualist insists that one’s soul always retains its own identity even as it is joined with god.