If we look back at the Pre-Mortal Existence, each of us lived as spirits with our Heavenly Father. We loved it there, but desired one thing more than any other: We wanted to be like our Heavenly Father.
Heavenly Father was different than us in two ways: He was perfect, and he had a body. We desired these two things, and our loving Heavenly Father created the Plan of Salvation so we could accomplish our goal and progress toward His level of existence.
Hence, we were sent to earth to gain experience in the physical, mortal realm, and to recieve a body. Here we have become subject to two things that we cannot overcome on our own: Spiritual Death and Physical Death.
Spiritual death is defined as our separation from God’s presence. This came by coming away from His presence and down to earth, and also from the fact that we are all sinners and fall short of the perfection He requires, for “no unclean thing can dwell with God.”
Spiritual death is overcome as we have faith and obey God’s word, but even then none of us will make it. To fully overcome it’s affects, we must accept the Atonement of Jesus Christ, who paid for our sins by taking them upon Himself, and apply His Atonement in our lives. Only through this can we be made clean and worthy to stand in God’s presence.
The second obstacle is Physical Death, for the Plan was created so we could be like God, and have a body like His.
Physical death is the separation of body and spirit. When we die, the body goes to the grave, and the spirit to a world of spirits, where we will await the resurrection.
Resurrection is the joining back together of body and spirit, the body being changed to an eternal nature that will never again die or suffer the frailties of the mortal flesh. It is made possible through the resurrection of Jesus Christ, who was the first to resurrect.
At the final judgement, all will be resurrected, their spirit and body brought back together, never to separate again. This is a free gift, through the resurrection of Christ, to all of God’s children who were born on the earth, regardless of whether they were good or bad.
“For since by man came death, by man came also the resurrection of the dead. For as in Adam all die, even so in Christ shall all be made alive.” (1 Corinthians 15:21-22)
“There shall be a resurrection of the dead, both of the just and unjust.” (Acts 24:15)