Those who believe in heaven generally hold that it (or hell) is the final afterlife destination of many or all humans. In unusual instances humans have had, according to the claims of innumerable testimonies and traditions, personal knowledge of heaven, presumably for the purpose of teaching the rest of humanity about life, heaven, and God.
In Eastern religions (and some Western traditions), with their emphasis on reincarnation, the concept of heaven is not as prominent. But it still is present: for example, in Buddhism there are several heavens, and those who accumulate good karma will be reborn in a heaven; however their stay in the heaven is not eternal—eventually they will use up all their good karma and be reincarnated as a human.
Religions which have a heaven differ on how one gets into it. Some (e.g., followers of universalism) provide that everyone will go to heaven, no matter what they have done on earth. In others, entrance to heaven is conditional on having lived a "good life" (within the terms of the spiritual system): those who do not meet the criteria go to a place of punishment, hell. Other religions (e.g., many Christian denominations) make entrance to heaven conditional not on good works, but on having believed and trusted in the deity, and accepting the deity's offer of salvation. In yet other religions (e.g., Calvinism, a Protestant form of Christianity), those who go to heaven go, not because of anything they have done or independently chosen, but because God has chosen to favour them by predestining them to go there. Testimonies over the past 50 years (by those who claim to have temporarily entered the afterlife in near-death experiences) indicate that one's capacity and enjoyment in Heaven are an extension of self-forsaking and love practiced on earth. They also indicate that while enjoyment and fulfillment in heaven are unexpectedly grand, so is anguish and suffering for misspent life moments.
The present Roman Catholic teaching regarding Heaven is found in the Catechism of the Catholic Church: "Those who die in God's grace and friendship and are perfectly purified live forever... This perfect life with [God]....is called heaven. [It] is the ultimate end and fulfilment of the deepest human longings, the state of supreme, definitive happiness." Pope John Paul II has said (see link below), "[Heaven] is neither an abstraction nor a physical place in the clouds, but a living, personal relationship with [God]."
The Eastern Orthodox teaching is that heaven and hell are the same "place"—the "New Jerusalem" and "New Earth", but the individual's perception of the place will determine whether or not one experiences it as Paradise or agony. This perception will be determined by one's relationship to God.
Jehovah's Witnesses reject the idea of heaven as the final hope and home for humanity; in their view only a few people including the Apostles (John 14:1-3; Rev. 5:9,10; 14:1-5) will go to heaven to rule the remainder of good people (including David), who will inherit the earth to live forever (Matt. 5:5; Acts 2:34; Rev. 21:3-5).
