The word gospel means good news. It’s the proclamation that God has made a way to forgive sinners (Romans 3:21-26). The very essence of the gospel is the wonderful truth that Christ became our substitute and was punished for our sin (1 John 4:10). The result is that anyone who repents of their sin and puts their faith in Christ, will be made righteous in the eyes of God.
God created a perfect world, and placed mankind in that world to bear his image and bring him glory. Tragically, he rebelled against his maker by believing a lie that God was withholding something good (Genesis 3:1-5). The liar was Satan, and the result was the introduction of sin into a perfect world.
Since God is absolutely holy and just, he was now obligated to destroy mankind and punish them forever. This would have been fine with Satan because all he cared about was destroying what God loves. However, before the world was even created God knew this would happen and had already made a plan to redeem some of those men (Ephesians 1:3-6).
So in an act of sacrificial love, God became man in order to live a sinless life, and then take their punishment on the cross. This inconceivable sacrifice was made so that we could get credit for his perfect life, and escape the wrath we all deserve (Romans 5:6-11).
Romans 10:9 says, “If you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you shall be saved”. God's justice demands death, but his love provides a Savior who chose to die instead (1 Peter 3:18). This satisfied God's justice, and Christ's perfect life satisfied the demands of God's holiness (2 Corinthians 5:21), enabling him to save us (Romans 3:26).
True faith is always accompanied by repentance, meaning we acknowledge our sin and turn away from it (1 Thessalonians 1:9-10). We follow Christ (Matthew 11:28-30), obey him (1 John 2:3), and live as he intended us to (Ephesians 2:10).