He who has an ear, let him hear what the Spirit says to the churches. He who overcomes will not be hurt by the second death. Revelation 2:11
So there is more than one death. In order to rightly divide the word we need to read what the Bible says about it. It is pretty simple, really.
When I taught Revelation, a man told me that he wanted to join my class. I talked with him about it. He said he had always wanted to understand this book. But when I asked him what he had read regarding Revelation, he replied, "Nothing. I wouldn't know where to get a book on it." Should I have told him to try a religious book store? There are some good books out there.
Fortunately for us, we really do not need a book on this subject, though. It is really a simple concept. In the normal course of life we all die once. But the blessed will not die after they are caught up to heaven. These are believers. They become immortal at the rapture. Death will never touch them again.
Not so for unbelievers though. They must be resurrected and face a trial at the Great White Throne judgement (Rev. 20:12). Those who are subject to this trial and are found guilty are cast into the Lake of Fire. Contrary to the belief of so many, this is not torture without end. It is the second DEATH.
Those who argue against annihilation say it is not so--they don't die. that second death only means separation from God. I ask, when were they ever united to Him?