As sinners, human beings are in need of both the forgiveness of God and reconciliation to him. The Scriptures use the term salvation to refer to the multifaceted work of God by which he rescues sinners from his wrath (Romans 5:6-9), forgives them (Ephesians 1:7), brings them back into relationship with himself (2 Corinthians 5:20), transforms their lives (2 Corinthians 3:18), and ultimately conforms them to be like Jesus (Romans 8:29).
God's purpose from the foundation of the world was to redeem a people for himself who would declare his excellencies on the earth and to be made holy (1 Peter 2:9-10). God saves such a people by calling them to himself (1 Corinthians 1:18-25, Romans 8:28-30), extending grace to them in the gospel, the good news of the saving work of Jesus Christ on an executioner's cross.
God sent his own Son into the world, to die the death we deserved, the death for sin and to live the life we could not live, a life without sin. God then raised Jesus from the dead declaring his work to be triumphant over sin, death and hell. In doing so the just penalty for our sins was taken by Jesus as our substitute and we receive new life (Romans 6:4) and his righteousness by faith (2 Corinthians 5:21). It is by God's grace, his kindness and goodness towards us, that we are saved (Ephesians 2:8, 9). Our lives are united with Christ and we continue to live in him while he continues to mold and change us, making us ever more like him in increasing ways. This process continues throughout our lives and moves forward as we exercise spiritual disciplines and put to death sin by those same means (Romans 8:13). We hold on to the hope of the promise that one day we will be glorified, fully changed and finally made perfect by God in the kingdom to come.
All of these things - forgiveness, reconciliation, redemption, and a changed life are free gifts and the work of God. They are not rewards for our own self-righteousness, nor are they earned by keeping religious or moral rules. The good news is that God accepts rebels home, loves them fully, adds them to his church and sends them in mission into their world. Only those who acknowledge their sin and great need can come to God in Christ - and all who come to him he will in no way cast out.