What does 1 Corinthians 15:47 mean?

What is the difference between the bodies of Christians as they are now, compared to the bodies we will be raised with after we are returned to life in the resurrection? Paul has been describing those differences in this section. Now he shows that these bodies are different in both their origin and what they were initially made from.

The first man seems to refer to people, in general, as we first exist. Each of us, as Adam's descendants, are from the earth. Adam was a man "of the dust" (Genesis 2:7), and all born after him are made of "earth stuff" designed to exist on the earth. The second version of us, though—the "second man"—is from heaven. Our resurrected bodies will be made of "heaven stuff" and built to exist eternally as do all who reside in heaven with God.

Another way to read this verse is to see the "first man" as Adam and the "second man" as Christ. The same ideas hold true in either case. All humans follow the pattern of Adam, and all Christians the pattern of Christ.