To answer your good question, let’s begin by reading Revelation 20:11-15, “And 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. And 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. And 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. And death and hell were cast into the lake of fire. This is the second death. And whosoever was not found written in the book of life was cast into the lake of fire.”

This scenario before us is what we know as the Great White Throne judgment.  This is when all the unsaved will be judged by God “according to their works.”  Everyone who has ever existed, and rejected the Lord Jesus Christ as their savior will stand before God on this great and terrible day to be judged for their sins.  We see from this that books were written to record every single act of sin that every individual committed.  The ‘dead, small and great’ speak of those who are spiritually dead…those who were never given life by believing on the Lord Jesus Christ.  We see clearly from 1 John 5:12 that, “He that hath the Son hath life; and he that hath not the Son of God hath not life.”

At this event, we see that ‘death and hell delivered up the dead that were in them.’  We also see that ‘death and hell were cast into the lake of fire.’  How are we to understand this?  There are two words that are normally translated as hell in the New Testament. 

GEHENNA – This is defined as a place of eternal burning, torment, misery.

HADES – According to Strong’s concordance and dictionary this refers to ‘the unseen, i.e. “Hades” or the place (state) of departed souls. 

I encourage you to use a good concordance and research the different times that GEHENNA or HADES is used and translated as Hell in the Bible.  They are definitely two things and are not the same.  In our portion in Revelation 20:13-14, the word translated Hell is HADES, not GEHENNA. 

We understand death to be the condition of the body after the soul and spirit leave it.  Hades is the condition of the soul and spirit while separated from the body.  When the believer dies, his soul and spirit immediately leave the body and go to be with the Lord as we read in 2 Corinthians 5:8, “We are confident, I say, and willing rather to be absent from the body, and to be present with the Lord.”

Realizing that, let’s look at your question about how “death and hell (Hades) were cast into the lake of fire.”  At the Great White Throne judgment, all those who have died in their sins will be resurrected and stand before the Lord to face His righteous judgment.  Death (the body) and Hades (the soul and spirit) will be rejoined, and upon judgment, will be cast into the lake of fire (Hell). 

For the believer, our soul and spirit shall be reunited with our body at what is called the Rapture of the church, which happens about 1007 years before the Great White Throne judgment.  We read in 1 Thessalonians 4:13-17, “But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope. For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him. For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep. For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.”

So, the believers will be raised and taken to Glory to be forever with the Lord.  Later, the unbelievers will be raised to be cast into the lake of fire to be forever tormented.  Today, if you have never received the Lord Jesus Christ as your savior, I plead with you to put your faith in Him for your salvation so that you will not be involved in that terrible judgment of God and be cast into the eternal lake of fire.  (CC)  (644.6)