The exact phrase "original sin" isn't found in the Bible, but over the centuries theologians have used it as a kind of "theological shorthand" to summarize a very important biblical truth.
What is this truth? It is the truth that we are all sinners, and we all have within us the tendency or inclination to do what is wrong. We aren't just sinners by choice; we are sinners because our hearts are turned away from God. To put it another way, sin is like an inherited disease–a spiritual disease that weakens us and keeps us from doing what is right. Even when we want to do good, we find we can't. The Apostle Paul put it this way: "For what I do is not the good I want to do; no, the evil I do not want to do–this I keep on doing" (Romans 7:19).
Adam and Eve were the first sinners, and their rebellion against God was the first (or original) sin. But their rebellious spirit has come down to us, and as the result, the Bible says, "All have sinned and fall short of the glory of God" (Romans 3:23). We all stand guilty before God, for we are sinners.
But this isn't the end of the story! God loves us in spite of our rebellion, and He sent His Son into the world to forgive us and give us new hearts. Sin has now been conquered by His death and resurrection! Has Christ forgiven your sins? Make sure by turning to Him and trusting Him alone for your salvation.