Like all verses, that verse is subject to more than one interpretation. It also needs to be understood in context.
Rev 20
12 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.
13 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.
14 And death and hell were cast into the lake of fire. This is the second death.
15 And whosoever was not found written in the book of life was cast into the lake of fire.
Much, perhaps most, of the Book of Revelation is symbolic, not literal. There is no lake that has flames of fire burning in it.
The first death is our physical death. The second death is spiritual death. Spiritual death is hell since it is distance from God.