Heaven is a place that seems absolutely perfect in every way. You can think of it as the lofty heavens up above, or as a place of everlasting bliss.
The places you think of as heaven could also be called "paradise" or "Eden." All of these words are based on a religious idea of heaven as a perfect, blissful existence that's granted to good people after they die. This spiritual heaven is generally depicted as the place where God lives, and is commonly described as being high in the sky. In fact, the original meaning of the Old English heaven, heofon, was "sky."