Mormonism teaches that when people die, their spirits enter the spirit world. This world is divided into two parts: paradise and spirit prison.
When Mormons remain faithful throughout their mortal lives, they will enter paradise in the spirit world until the day of judgment when their bodies will be resurrected with their spirit. In paradise, they will continue to progress toward eternal life. This work will mainly include going on missions to reach those in spirit prison and converting them to Mormonism.
“Paradise is that part of the spirit world in which the righteous spirits who have departed from this life await the resurrection of the body. It is a condition of happiness and peace.” (Gospel Topics: Paradise, lds.org)