Physical death and spiritual death (separation from God) are natural consequences of mortal life, but they are not permanent. Immortality is given, and eternal life is possible, for every person because of the Atonement of Jesus Christ. Read more at ChurchofJesusChrist.org/topics/salvation.
When Adam and Eve ate the forbidden fruit in the Garden of Eden, they became mortal, meaning they would die (physical death) and they were separated from God (spiritual death). These would have been permanent conditions if not for the Atonement of Jesus Christ.
Christ was resurrected three days after His Crucifixion. Because of that, all people will also be resurrected, meaning their body and spirit will be reunited. Resurrection and immortality are gifts given to everyone, no matter what.
Spiritual death, or separation from God, requires more effort to overcome. For all people, it is possible but not guaranteed. Jesus Christ’s Atonement makes it possible, but to access the power of His Atonement, one must choose to repent of one’s sins, live the commandments, and follow Christ. Eternal life, also referred to as exaltation, offers the blessings of the highest degree of heaven.
God’s work and glory is to bring about immortality and eternal life for all His children. We can permanently overcome both physical and spiritual death to live with Him and His Son, Jesus Christ, again.