The Gospel (i.e., Good News) is that the Lord Jesus Christ, humbled Himself by taking on human flesh (Hebrews 2:14-18; Philippians 2:6-9), He fulfilled the Law perfectly (Matthew 5:17) and offered Himself as a sinless sacrifice, “He died for sins once for all, [the] just for [the] unjust, in order that He might bring us to God, having been put to death in the flesh, but made alive in the spirit; (1Peter 3:18 - NASB)
What makes the Gospel good news is that the Lord Jesus Christ has done everything necessary through His life, death and resurrection to remove every obstacle that separates us from a holy God. Because of the atoning work of the Lord Jesus, we, by God’s grace alone through faith alone in Christ alone, can be reconciled to God to enjoy Him forever.
There is no salvation apart from believing the Gospel (John 1:12; 14:6; Acts 4:12; 16:31).
1 Corinthians 15:1-4
1 Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand,
2 by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain.
3 For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures,
4 and that He was buried, and that He was raised on the third day according to the Scriptures,
13Christ redeemed us from the curse of the Law, having become a curse for us-- for it is written, “Cursed is everyone who hangs on a tree”--
14 in order that in Christ Jesus the blessing of Abraham might come to the Gentiles, so that we might receive the promise of the Spirit through faith.
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.
17 For in it [the] righteousness of God is revealed from faith to faith; as it is written, “But the righteous [man] shall live by faith.”
8 For by grace you have been saved through faith; and that not of yourselves, it is the gift of God;
9 not as a result of works, so that no one may boast.