Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come. —Romans 5:14 ESV
Adam is a “type” of him who was to come, Christ.
What does “type” mean? The NIV says “pattern.” Adam was a pattern of Christ who was to come. He was an example, or a foreshadowing, or a prefiguring of Christ. Let me see if I can say it so that the children can understand it. Sometimes when we want to understand something better we compare it with something like it, but not totally like it. For example, if you come to my house and I say, “Look at my dog, Sable, and tell me what you see,” you might say, “She’s black with white paws and brown eyes and a tail with a white tip.” And that may be about it. But then I go get Pastor Livingston’s dog, Lady, and put her beside my dog and say, “Now how is my dog different? What do you notice that you didn’t notice before?” Then you might say, “Well, Sable is bigger, and Lady seems to be friskier and Sable is sort of laid back, and Lady’s tail kind of hangs down and Sable’s curls up. And Lady has long hair and Sable has short hair. And Lady’s nose is thinner.” So do you see what happens: you notice new things about Sable when you compare her with another dog that is different – the size, the temperament, the curl of the tail, the length of hair, the thickness of the nose. So one way to see something better is to see it alongside something like it but different.
That is what Paul is doing in this paragraph. In verse 14 he says he is going to view Christ in comparison and contrast with Adam. That makes Adam a type or a pattern. And the aim is to see more clearly and more fully and more deeply the work of Christ and how he became the foundation of our justification.