What is the gospel? The gospel message is “good news”. What is the good news? Without a doubt, despite the fact that this message has now been exchanged for other messages very distant from what the Gospel really is, it is a message of good news, and the good news is that Christ came and died on the cross, and rose again to save sinners.
The Word of God says in Romans 1: 16-17
16 For I am not ashamed of the gospel, because it is the power of God that brings salvation to everyone who believes: first to the Jew, then to the Gentile.
17 For in the gospel the righteousness of God is revealed—a righteousness that is by faith from first to last, just as it is written: “The righteous will live by faith.”