When people die, Mormons believe their spirits enter the spirit world. It is divided into two parts: paradise and spirit prison. Mormon spirits go to paradise, while non-Mormon spirits go to spirit prison. In paradise, Mormons can continue their progression towards godhood; from there they can go on missions to spirit prison in order to convert non-Mormon spirits to Mormonism.
Christians often point to Jesus’ statement to the thief on the cross, “Today you will be with me in paradise” as proof of salvation without works. Mormons, however, believe that Jesus told the thief he would go to the paradise of the spirit world where he would have to work on progressing.
Biblical Christianity teaches that paradise is a term for heaven itself. Compare Revelation 22:2 and its reference to the tree of life with Revelation 2:7. From this it becomes obvious that Jesus, in Luke 23:43, told the thief on the cross he would be with Jesus in heaven.