What is Hell ?

The following is taken from the Bible Dictionary.

Hell   An English translation of the Hebrew word Sheol, hell signifies an abode of departed spirits and corresponds to the Greek Hades. 

In common speech it generally denotes the place of torment for the wicked, although it has been often held, both in the Jewish and the Christian churches, that Hades (meaning broadly the place of all departed spirits) consists of two parts, paradise and Gehenna, one the abode of the righteous and the other of the disobedient.

“Gehenna,” or “Gehenna of fire,” is the Greek equivalent of the “valley of Hinnom,” a deep glen of Jerusalem where the idolatrous Jews offered their children to Moloch (2 Chr. 28:3; 33:6; Jer. 7:31; 19:2–6). It was afterwards used as a place for burning the refuse of the city (2 Kgs. 23:10), and in that way became symbolical of the place of torment (Matt. 5:22, 29–30; 10:28; 18:9; 23:15, 33; Mark 9:43, 45, 47; Luke 12:5; James 3:6). Expressions about “hell-fire” are probably due to the impression produced on men’s minds by the sight of this ceaseless burning, and are figurative of the torment of those who willfully disobey God.

In latter-day revelation hell is spoken of in at least two senses. One is the temporary abode in the spirit world of those who were disobedient in this mortal life. It is between death and the resurrection, and persons who receive the telestial glory will abide there until the last resurrection (D&C 76:84–85, 106), at which time they will go to the telestial glory. In this sense the Book of Mormon speaks of spiritual death as hell (2 Ne. 9:10–12). Hell, as thus defined, will have an end, when all the captive spirits have paid the price of their sins and enter into a degree of glory after their resurrection. Statements about an everlasting hell (Hel. 6:28; Moro. 8:13) must be interpreted in their proper context in the light of D&C 19:4–12, which defines eternal and endless punishment.

On the other hand, the devil and his angels, including the sons of perdition, are assigned to a place spoken of as a lake of fire—a figure of eternal anguish. This condition is sometimes called hell in the scriptures (2 Pet. 2:4; D&C 29:38; 88:113). This kind of hell, which is after the resurrection and judgment, is exclusively for the devil and his angels, and is not the same as that consisting only of the period between death and resurrection. The one group are redeemed from hell and inherit some degree of glory. The other receive no glory. They continue in spiritual darkness. For them the conditions of hell remain.