Death, or the literal separation of our body and our spirit, is unavoidable. However, death is not the end. Death is merely a step on the path. After death, our spirit enters the spirit world (Ecclesiastes 12:7), which is divided with two commonly-known distinctions: heaven and hell. In the scriptures, heaven and hell are also referred to in many ways including as paradise and prison. Essentially, all those who accepted the gospel of Jesus Christ while on this Earth go to paradise and everyone else goes to prison. The prophet Alma wrote:
"Now, concerning the state of the soul between death and the resurrection—Behold, it has been made known unto me by an angel, that the spirits of all men, as soon as they are departed from this mortal body, yea, the spirits of all men, whether they be good or evil, are taken home to that God who gave them life. And then shall it come to pass, that the spirits of those who are righteous are received into a state of happiness, which is called paradise, a state of rest, a state of peace, where they shall rest from all their troubles and from all care, and sorrow. And then shall it come to pass, that the spirits of the wicked, yea, who are evil—for behold, they have no part nor portion of the Spirit of the Lord; for behold, they chose evil works rather than good; therefore the spirit of the devil did enter into them, and take possession of their house—and these shall be cast out into outer darkness; there shall be weeping, and wailing, and gnashing of teeth, and this because of their own iniquity, being led captive by the will of the devil" (Alma 40:11-13).However, a residence in heaven or hell is not the end. Because God is a merciful God, he still has provided a way that those in hell might be saved. After Christ was crucified, he visited hell, or spirit prison, and began to preach his gospel (1 Peter 3:18-20). This preaching goes on today (Doctrine and Covenants 138). Christ began this teaching in spirit prison so everyone who has ever lived will have an opportunity to choose to accept or reject his gospel, so that they might be judged according to the laws God has given us upon this Earth (1 Peter 4:6).
We will live in the spirit world until the resurrection when, just as Jesus Christ did, our physical body of flesh and bones will be reunited with our spirit in an immortal, perfect state (1 Corinthians 15). This is only possible through the Atonement of Jesus Christ, because Christ exercised power over death. Resurrection is a free gift given to us by our Savior that all people receive, whether they are righteous or wicked.
Once we are resurrected, we are judged as to our works and the intentions of our hearts at the great and final judgment. In the Apostle John's words:
"And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works" (Revelation 20:12-13).This judgment results in our reward for our performance in mortality where we made many choices. It determines where we will reside as immortals. There are three kingdoms of glory where we have the opportunity to reside called: celestial, terrestrial, and telestial. Paul taught the Corinthians about these kingdoms, "There are also celestial bodies, and bodies terrestrial: but the glory of the celestial is one, and the glory of the terrestrial is another. There is one glory of the sun, and another glory of the moon, and another glory of the stars: for one star differeth from another star in glory" (1 Corinthians 15:40-41). In other words, the greatest glory, reserved for those that fully accepted the gospel of Jesus Christ and his Atonement, strove to keeps his commandments, and received all of the saving ordinances, is in the celestial kingdom, or the glory of the sun. Those who lived honorable lives, but did not accept the gospel of Jesus Christ go to the glory of the moon or the terrestrial kingdom. Those who continued to sin unrepentantly receive the telestial kingdom, compared in glory to the stars, relative to the sun and the moon.
Paul also implies that there are multiple degrees of glory within each kingdom "for one star differeth from another star in glory". This statement makes so much sense to me. The idea of a clear-cut heaven and hell in the end does not make a whole lot of sense, in my opinion. Where would that line be drawn? Rather, our merciful Heavenly Father has given us the Plan of Happiness where we will be rewarded according to our faith and our works (James 2:17-26). We are blessed in the life after this based on our individual performance, we are not simply lumped into one of two groups.
I know that the Plan of Salvation is true doctrine. I feel assured that when I die or when those I know and love die, all is well. If you have even been to a Mormon funeral, you would see a total difference in the minds and moods of the attendees for this very reason--we know what happens after death! I know that Heavenly Father and Jesus Christ have prepared three distinct kingdoms for us. I know these things because I have asked God in prayer and he has brought peace to my soul, he has given me an assurance of the truth of the Plan of Salvation. I share this testimony with you in the name of Jesus Christ. Amen.