Remission of sin, absolution from guilt, and freedom from punishment are part of justification. Justification is an act of God's grace. It begins in His free, unmerited favor, and it is given to us as part of our union with Christ by faith. In order to be justified, a person must be given a righteousness equivalent to God's perfect righteousness. Hence, imputation precedes justification.
Imputation is the charging to the account of one person something which properly belongs to another.
The Lord Jesus Christ shares his perfect righteousness with the believer, Rom. Abraham believed God and it was imputed to him for righteousness. Hence, imputation of righteousness on the basis of faith brings about justification. The means of justification is redemption, Rom. Being justified freely by his grace through the redemption that is in Christ Jesus.