“Forgiveness of sins and justification are good news because they remove obstacles to the only lasting, all-satisfying source of joy: Jesus Christ. Jesus Christ is not merely the means of our rescue from damnation; he is the goal of our salvation. If he is not satisfying to be with, there is no salvation. He is not merely the rope that pulls us from the threatening waves; he is the solid beach under our feet, and the air in our lungs, and the beat of our heart, and the warm sun on our skin, and the song in our ears, and the arms of our beloved.” ~ John Piper
I for one am beyond stoked that you are asking this question. There truly is no more colossal of an inquiry that you could ever make.
What is the Gospel? The Gospel begins with God. He is all that is perfect and lovely, holy and flawless. He alone is eternal, omnipotent, infinite, omniscient, immortal, and omnipresent. All that He loves is righteous. That which He despises is sin.
In rebellion against this holy One mankind revolted, thinking, doing, and speaking that which shamed God. All of humanity – from the aged to the infant, the religious to the rebel – have sinned and brought displeasure to the eternal Sovereign. Consequently, this transgression has cut us off from God, isolating us from the communion with Him that we desperately need. We are condemned justly and sentenced, under His wrath, to eternal destruction. Such is the plight of every man, woman, teen, and child.
However, God, the Just King, is abundantly rich in mercy. To reconcile sinful creatures to Himself, He sent His eternal Son, Jesus Christ, who is also God, into this world. Jesus became a man, lived without any trespass, and died a brutal death by crucifixion in order to pay the penalty for the sins of all who will be saved. Three days following His death, Jesus physically rose from the dead, conquering death, sin, and hell for us, and now offers us liberation from and forgiveness of sin in exchange for His perfection. Your responsibility, my friend, is to turn from your selfishness (the Bible calls this repentance) and to take hold of the gift of grace through trust in the Person and work of Jesus for you.
The Bible makes it clear that we are justified not by our works, not by our efforts, not by our deeds, but by faith – and by faith alone. The only way you can receive the benefit of Christ’s life and death is by putting your trust in Him – and in Him alone. Through that faith, by His grace, through the work of Jesus you are declared just by God, you are adopted into His family, you are forgiven of all of your sins, and you have begun your pilgrimage for eternity.