What does the concept of 'justification' mean in Christianity?

In Christianity, justification refers to the legal declaration by God that a sinner is considered righteous because of their faith in Jesus Christ. This concept is most clearly laid out in Romans 5:1, stating that 'having been justified by faith, we have peace with God through our Lord Jesus Christ.' Justification is not based on any works or merits of the individual; rather, it is by God's grace alone. In Acts 13:39, it is affirmed that through Him, everyone who believes is justified from all things from which they could not be justified by the law. This reflects the core of the Gospel that through Christ's sacrificial death and resurrection, believers are acquitted from guilt and receive a righteous standing before God.