Heaven is generally the name that religious people give to the place where good people go after they die.

Paradise is the name of the garden where, in the Bible story, Adam and Eve lived before they sinned and were forced to live as mortal humans.

Sometimes these words are used in almost the same way when we talk about things in daily life, but generally, the word "heaven" is used for a nice place you can go to after you die, and "paradise" is a place you can go to before you die.