Perhaps, it's the question you have always wondered about.  In short,  the word gospel means “good news,” so the gospel of Christ is the good news of His coming to provide forgiveness of sins for all who will believe.  The famous verse in the Bible says: "For God so loved the world, that he gave his only begotten Son, that whosoever believeth on him should not perish, but have eternal life."  Let's dive into a more detailed explanation.