This explanation of the difference between justification and sanctification is from the Westminster Larger Catechism.
Q. 77. Wherein do justification and sanctification differ?
A. Although sanctification be inseparably joined with justification, yet they differ, in that God in justification imputeth the righteousness of Christ; in sanctification his Spirit infuseth grace, and enableth to the exercise thereof; in the former, sin is pardoned; in the other, it is subdued: the one doth equally free all believers from the revenging wrath of God, and that perfectly in this life, that they never fall into condemnation; the other is neither equal in all, nor in this life perfect in any, but growing up to perfection.