In religious mythology, a place where you go when you die if you follow the instructions of your belief system. For example, certain sects of Christianity believe that the only requirement is accepting Jesus as your savior, while others believe that keeping the Ten Commandments, doing good works, confessing sins, and/or a number of other requirements must also be met.
The concepts of heaven and hell are the basis for Pascal's Wager.
Heaven and Hell are frequently used to reconcile the inability for humanity to mete out justice during corporeal life. The idea is that even if one can get away with violating human laws, a divine witness/victim/judge/jury/executioner will ensure that no one can avoid perfect justice.