God created all things. This includes the universe, the world, and all life in the world. God is the ruler and king of all that he has made. Everything that God created was originally good. In particular, God created men and women to live in the world, and to live in relationship with him as God and king of the universe. Men and women are created in the image of God. They are special. Whoever you are you matter to God.
Humanity chose to break this relationship with God. Collectively and individually humanity tends away from living to please God towards living to please ourselves. This natural tendency to ignore God and rebel against God is called sin. Whatever its origins sin is a problem for the world because it constitutes our break with God. Whether we like it or not humanity is struggling with the effects and the implications of sin.
God does not ignore sin and its consequences. In fact, according to the gospel, God has acted and is acting to restore the world. God does this in all his actions. He has done it supremely through the life, death, and resurrection of Jesus Christ. Jesus lived to fulfil human potential in relation to God. In his death he took away the sin of the world. He rose to life as a demonstration that those who look to him and believe the gospel are reconciled to God. Jesus Christ is God’s judge, and he is overseeing God’s restoration of all things. He will return to complete this work to establish his kingdom rule on earth forever.
What if I believe this gospel? Those who believe that Jesus is Lord and judge of all receive the forgiveness of their sins. They enter into a new relationship with God, and they can look forward to life in God’s recreated world. This new relationship begins the moment we believe the gospel. Physical death no longer means the end of life, but the beginning of a new stage in this new relationship.
What if I do not? Christians do not really like to think about this question, but the gospel forces us to reckon with it. The broadest and easiest thing to write is this: those who do not believe the gospel of Jesus Christ remain in their broken relationship to God. They reject the new relationship that is offered. In and beyond physical death that broken relationship is confirmed through eternal separation from God's blessing and goodness.