Boyd’s Bible Dictionary:
Place of departed spirits
Greek equivalent of Hebrew “sheol,” unseen world. Hell in A. V.; Hades in R. V. (Matt. 11:23; 16:1823And thou, Capernaum, which art exalted unto heaven, shalt be brought down to hell: for if the mighty works, which have been done in thee, had been done in Sodom, it would have remained until this day. (Matthew 11:23)
18And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. (Matthew 16:18); Acts 2:3131He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. (Acts 2:31); Rev. 1:1818I am he that liveth, and was dead; and, behold, I am alive for evermore, Amen; and have the keys of hell and of death. (Revelation 1:18)).
Concise Bible Dictionary:
From Anstey’s Doctrinal Definitions:
“Sheol” and “Hades” refer to the same thing; Sheol is Old Testament Hebrew and Hades is New Testament Greek. (See the J. N. Darby Translation footnote on Psalm 6:55For in death there is no remembrance of thee: in the grave who shall give thee thanks? (Psalm 6:5).) Sheol/Hades is the world of unseen disembodied souls and spirits into which deceased believers and unbelievers pass, without specifying what condition they are in. (See the J. N. Darby Translation footnote on Matthew 11:2323And thou, Capernaum, which art exalted unto heaven, shalt be brought down to hell: for if the mighty works, which have been done in thee, had been done in Sodom, it would have remained until this day. (Matthew 11:23).) The gospel has brought to light “life and immortality” (2 Tim. 1:1010But is now made manifest by the appearing of our Saviour Jesus Christ, who hath abolished death, and hath brought life and immortality to light through the gospel: (2 Timothy 1:10)), and as a result, we now know that there are two opposing conditions in Sheol/Hades: "torments" for the lost (Luke 16:24-2524And he cried and said, Father Abraham, have mercy on me, and send Lazarus, that he may dip the tip of his finger in water, and cool my tongue; for I am tormented in this flame. 25But Abraham said, Son, remember that thou in thy lifetime receivedst thy good things, and likewise Lazarus evil things: but now he is comforted, and thou art tormented. (Luke 16:24‑25)) and bliss ("paradise" –“the garden of delights”) for believers (Luke 23:4343And Jesus said unto him, Verily I say unto thee, To day shalt thou be with me in paradise. (Luke 23:43)).
What can be confusing is that Hades is erroneously translated as "hell" eleven times in the KJV (Matt. 11:23; 16:1823And thou, Capernaum, which art exalted unto heaven, shalt be brought down to hell: for if the mighty works, which have been done in thee, had been done in Sodom, it would have remained until this day. (Matthew 11:23)
18And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. (Matthew 16:18); Luke 10:15; 16:2315And thou, Capernaum, which art exalted to heaven, shalt be thrust down to hell. (Luke 10:15)
23And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom. (Luke 16:23); Acts 2:27, 3127Because thou wilt not leave my soul in hell, neither wilt thou suffer thine Holy One to see corruption. (Acts 2:27)
31He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. (Acts 2:31); 1 Cor. 15:5555O death, where is thy sting? O grave, where is thy victory? (1 Corinthians 15:55) – margin; Rev. 1:18; 6:8; 20:13, 1418I am he that liveth, and was dead; and, behold, I am alive for evermore, Amen; and have the keys of hell and of death. (Revelation 1:18)
8And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth. (Revelation 6:8)
13And 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. 14And death and hell were cast into the lake of fire. This is the second death. (Revelation 20:13‑14)). Each one of these references should be translated "Hades." Consulting a critical translation, such as the J. N. Darby Translation, clears this up immediately.
A query was submitted to the editor of Help and Food magazine concerning Hades: "Ques. What is Hades? Ans. Unquestionably it is the whole unseen world, including both saved and lost. See Luke 16:2323And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom. (Luke 16:23); Revelation 20:13-1413And 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. 14And death and hell were cast into the lake of fire. This is the second death. (Revelation 20:13‑14), for the lost, and Acts 2:27, 3127Because thou wilt not leave my soul in hell, neither wilt thou suffer thine Holy One to see corruption. (Acts 2:27)
31He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. (Acts 2:31) for our blessed Lord. Hades answers to Sheol in the Old Testament" (Help and Food, vol. 14, p. 140). We would add to these references 1 Corinthians 15:5555O death, where is thy sting? O grave, where is thy victory? (1 Corinthians 15:55), which indicates that believers who have died are in Hades. The KJV renders it “grave” in this verse, but the word in the Greek is “Hades” and should be translated as such (J. Green’s Interlinear; Wigram’s Englishman’s Greek Concordance; Strong’s Concordance, etc.).
Sheol/Hades is a temporary state. All in this intermediate or separate state, into which death brings a person, will be resurrected—both believers and unbelievers—but at different times. (See Resurrection.) All who have died in faith are "unclothed" in Hades (2 Cor. 5:44For we that are in this tabernacle do groan, being burdened: not for that we would be unclothed, but clothed upon, that mortality might be swallowed up of life. (2 Corinthians 5:4)). Their souls and spirits are "with Christ" (Phil. 1:2323For I am in a strait betwixt two, having a desire to depart, and to be with Christ; which is far better: (Philippians 1:23)) in “paradise” (Luke 23:4343And Jesus said unto him, Verily I say unto thee, To day shalt thou be with me in paradise. (Luke 23:43)). This is in heaven because Scripture says that that is where Christ is (Luke 24:5151And it came to pass, while he blessed them, he was parted from them, and carried up into heaven. (Luke 24:51); Acts 1:9-10; 3:21; 7:559And when he had spoken these things, while they beheld, he was taken up; and a cloud received him out of their sight. 10And while they looked stedfastly toward heaven as he went up, behold, two men stood by them in white apparel; (Acts 1:9‑10)
21Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began. (Acts 3:21)
55But he, being full of the Holy Ghost, looked up stedfastly into heaven, and saw the glory of God, and Jesus standing on the right hand of God, (Acts 7:55); Phil. 3:2020For our conversation is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ: (Philippians 3:20); Heb. 4:1414Seeing then that we have a great high priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession. (Hebrews 4:14)). Paul confirms this, stating that when he was disembodied, he was in “paradise” in “the third heaven” (2 Cor. 12:2-42I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven. 3And I knew such a man, (whether in the body, or out of the body, I cannot tell: God knoweth;) 4How that he was caught up into paradise, and heard unspeakable words, which it is not lawful for a man to utter. (2 Corinthians 12:2‑4)). The Lord also taught that the disembodied souls and spirits of children who have died under the age of responsibility go straight to "heaven" (Matthew 18:1010Take heed that ye despise not one of these little ones; for I say unto you, That in heaven their angels do always behold the face of my Father which is in heaven. (Matthew 18:10) – "their angels" is a reference to their disembodied spirits; see Acts 12:1515And they said unto her, Thou art mad. But she constantly affirmed that it was even so. Then said they, It is his angel. (Acts 12:15)). The bodies of these disembodied persons, however, currently lay in the grave.
The souls and spirits of all who have died without faith are also in Hades, but they are in “torments” (Luke 16:2323And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom. (Luke 16:23)). They will remain in that state until the end of time, at which time they will be resurrected and judged for their sins at the “great white throne” (Isa. 24:2222And they shall be gathered together, as prisoners are gathered in the pit, and shall be shut up in the prison, and after many days shall they be visited. (Isaiah 24:22); Rev. 20:11-1511And I saw a great white throne, and him that sat on it, from whose face the earth and the heaven fled away; and there was found no place for them. 12And 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. 13And 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. 14And death and hell were cast into the lake of fire. This is the second death. 15And whosoever was not found written in the book of life was cast into the lake of fire. (Revelation 20:11‑15)). They will then be cast into “the lake of fire,” which is Hell. Hence, contrary to what is commonly thought, those who have died in their sins are not in Hell yet, and when they are put there, they will not be dead. They will be raised to life again and cast there alive! (Rev. 20:5; 135But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection. (Revelation 20:5)
5And there was given unto him a mouth speaking great things and blasphemies; and power was given unto him to continue forty and two months. (Revelation 13:5))