“Whoever believes in him is not condemned, but whoever does not believe stands condemned already because they have not believed in the name of God’s one and only Son” (John 3:18).
What is the gospel? Let's sum up what we've learned so far.
The God who spoke the universe into existence, who needs nothing at all, made human beings to know him and have a relationship with him. But when we sinned — and whenever we sin — we created a separation between us and him. We became something that cannot exist in his presence and someone whose company he cannot abide. We also joined in the treason of the fallen angels. The punishment for treason is death, but all the treasonous beings were designed to be immortal, so hell was created as a way to isolate the contagion and punish the guilty. When we joined their rebellion, we joined their fate.
But God, who is rich in mercy, chose to create a way for us to escape that fate. God became a man. As Jesus, he lived the perfect life we owe our creator. Then he was put to death on the cross, his sinless death being accepted as a payment for the debt we owe for our crimes.
Then he rose from the dead, not only proving that he was who he claimed to be, but also defeating death, showing what will happen to those who trust in him. Through him we can be reconciled to the God who made us to be with him.
To escape hell, all we have to do is live a perfectly sinless life from the moment of our conception to the moment of our death. Or we can place our hope in the death and resurrection of Jesus to pay the penalty for our sins.
When you trust in Jesus, you are united with Christ. Your sins are forgiven and forgotten. The Spirit of God transforms you into something new, making you someone that seeks God and can live with God. And you are adopted as a child and heir of that God.
One day every human being will stand before God’s judgement. Those who have not trusted in Christ will be held responsible for their own sins; they will be found guilty and “thrown into the outer darkness” where there will be “weeping and gnashing of teeth (Matt 8:12). Those who have placed their trust in Christ will be found not guilty, because Christ has taken their sin. They will see the results of their adoption in Christ, becoming heirs of God, reigning with him in his renewed kingdom forever.