The Gospel is the good news of Jesus's life, death, and resurrection:
1 Corinthians 15:1-4
"Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, [2] and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain. For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures,"
The Gospel is the power of God for salvation:
Romans 1:16
"For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek."
The Gospel brings us salvation as a gift to those who have faith in Jesus:
Ephesians 2:8-9
"For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast."