What is the difference between salvation and justification?
The term salvation within Catholic theology tends to emphasize the idea that we are rescued by Jesus from sin and its eternal consequences. The Catechism defines salvation as such:
The forgiveness of sins and restoration of friendship with God, which can be done by God alone (Glossary, Salvation).
The concept of justification within Catholic theology emphasizes right relationship with God. But rather than God merely declaring us to be in good standing with him, he actually makes us holy. The Catechism highlights this in its definition justification:
The gracious action of God which frees us from sin and communicates “the righteousness of God through faith in Jesus Christ” (Rom. 3:22). Justification is not only the remission of sins but also the sanctification and renewal of the interior man (Glossary, Justification).
In light of these two definitions, we can say that the Catholic understanding of salvation (rescued from sin and its eternal consequences) involves justification (right relationship with God and renewed within) and that justification involves salvation.