Simply put, gospel means good news. It is good news because it tells us that God loves us enough to take the initiative to save us. We cannot save ourselves. We need God's grace and mercy. This is why Christ came to this earth to die on a cross on our behalf.
"For our sake He made Him to be sin who knew no sin, so that in Him we might become the righteousness of God" (2 Corinthians 5:21).
The Gospel tells us that Christ was crucified, buried, raised on the third day, that He ascended into heaven, that He is at the right hand of God serving as our high priest, and that He will come again to this earth.
The Gospel reminds us that if we will transfer our trust to Christ, repent of our sins, and place our eternal hope in Him, we can be eternally saved. The Gospel teaches us that we can give Christ our sins and receive His righteousness.