What does it mean that Christ's righteousness is imputed to believers?

Imputed righteousness is a cornerstone of Reformed theology, teaching that Christ's righteousness is credited to believers through faith. This doctrine emphasizes that believers are not justified by their works but by the righteousness of Christ alone, as reflected in 2 Corinthians 5:21, which states that God made Him who knew no sin to be sin for us, so that in Him we might become the righteousness of God. This imputed righteousness is a gift from God, allowing sinners to be declared righteous and fully accepted before Him, thereby fulfilling the requirements of the law on their behalf. It underscores the depth of God's grace in providing everything necessary for salvation.