From a Christian position, heaven is the direct realm of God whereby His goodness (read 'glory')is fully displayed and enjoyed. The recipient of 'heaven' would experience perfect closeness to the great love of God, joy, peace, happiness, clarity.
Probably no harps or fluffy clouds or Warren Beaty.
CS Lewis heard of someone's concern that she might not 'want' heaven. Lewis replied that we've never wanted anything else.
Hell is a privation: a 'lack' of the goodness of heaven. Thus, loneliness, horror, unmitigated fear, pain, madness.
Hell is really, really bad. Why do you think they call it hell?