Rescued from what?
In the Bible, salvation means deliverance or rescue. Humanity's deepest problem is sin: all people fall short of God's goodness, and sin leads to death (Romans 3:23; Romans 6:23). This is more than making bad choices now and then. It is a broken relationship with the God who made us.
God does not leave people there. Salvation is his work of bringing people back to himself, forgiving their sin and freeing them for a new way of life. Jesus described this rescue as receiving eternal life rather than perishing (John 3:16).
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
What Jesus has done
The centre of Christian salvation is Jesus Christ. While people were still sinners, Christ died for them, showing God's love in action (Romans 5:8). Paul summarised the heart of the gospel by saying that Christ died for sins, was buried, and rose again on the third day (1 Corinthians 15:3-4).
Christians believe Jesus' death deals with sin and his resurrection defeats death. So salvation is not mainly self-improvement or religious effort. It rests on what Jesus has done, not on a person's ability to make themselves worthy.
Grace received through faith
Grace means God's undeserved kindness. Paul tells the Christians in Ephesus that they were saved by grace through faith, and that this was not something they could boast about achieving (Ephesians 2:8-9). Titus makes the same point: God saves people because of his mercy, not because they have first done enough righteous deeds (Titus 3:5).
Faith is trusting Jesus, turning towards him, and relying on him rather than on yourself. When the Philippian jailer asked Paul and Silas what he needed to do to be saved, they pointed him to belief in the Lord Jesus (Acts 16:31). The New Testament also connects faith with openly acknowledging Jesus as Lord (Romans 10:9-10).
For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.
A new life, not just a future promise
Salvation includes the hope of life with God beyond death, but it begins in the present. Jesus calls people to repent and believe the gospel (Mark 1:15). Repentance means a real turning of heart and direction, not pretending that sin does not matter. Good works do not purchase salvation, yet a life touched by God's grace begins to bear different fruit.
Christians have sometimes differed over how baptism relates to salvation and how to describe the stages of becoming more like Christ. Still, they broadly confess that salvation comes through Jesus, is received by faith, and leads into a life of following him. Jesus speaks of his sheep hearing his voice and of his lasting care for them (John 10:27-28). If you are exploring this, read one of the Gospels and consider Jesus' invitation for yourself.