Latter-day revelations speak of hell in at least two ways. First, it is another name for spirit prison, a temporary place in the postmortal world for those who died without a knowledge of the truth or those who were disobedient in mortality. Second, it is the permanent location of Satan and his followers and the sons of perdition, who are not redeemed by the Atonement of Jesus Christ.
Spirit prison is a temporary state in which spirits will be taught the gospel and have the opportunity to repent and accept ordinances of salvation that are performed for them in temples (see Doctrine and Covenants 138:30–35). Those who accept the gospel may dwell in paradise until the Resurrection. After they are resurrected and judged, they will receive the degree of glory of which they are worthy. Those who choose not to repent but who are not sons of perdition will remain in spirit prison until the end of the Millennium, when they will be freed from hell and punishment and be resurrected to a telestial glory (see Doctrine and Covenants 76:81–85).
Those who are not redeemed by the Atonement are in outer darkness, which is the dwelling place of the devil, his angels, and the sons of perdition (see Doctrine and Covenants 29:36–38; 76:28–33). Sons of perdition are those who receive “no forgiveness in this world nor in the world to come—having denied the Holy Spirit after having received it, and having denied the Only Begotten Son of the Father, having crucified him unto themselves and put him to an open shame” (Doctrine and Covenants 76:34–35; see also Doctrine and Covenants 76:31–33, 36–37). Such individuals will not inherit a place in any kingdom of glory; for them the conditions of hell remain (see Doctrine and Covenants 76:38; 88:24, 32).
“Hell,” True to the Faith
“Hell,” Encyclopedia of Mormonism
“What Happens after We Die?” mormon.org
“I Have a Question,” Ensign, April 1986
“Three Degrees of Glory,” The Mormon Channel Q&A, episode 11