Justification

Because man rebelled against God and entered into sin, there is a separation between man and God. We are all sinners by nature and are therefore condemned by a just, holy and righteous God.

As it is written, There is none righteous, no, not one: There is none that understandeth, there is none that seeketh after God. They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one.
Romans 3:10-12

The only way for us to be reconciled back to God is for Him to transfer our guilt upon Himself. The death of Jesus Christ made this transfer, forgiveness and reconciliation a possibility.

For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.
2 Corinthians 5:21

We receive justification by the grace of God (Romans 3:24, Titus 3:7), through the blood of Jesus Christ (Romans 5:9, Hebrews 9:22), and by faith (Romans 5:1-2, Galatians 2:16).

Justification results in the following:

Removal of the penalty of sin:
Saying, Blessed are they whose iniquities are forgiven, and whose sins are covered.
Romans 4:7

Removal of condemnation:
There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
Romans 8:1

Peace with God:
Therefore being justified by faith, we have peace with God through our Lord Jesus Christ:
Romans 5:1

The righteousness of Jesus Christ is ours:
For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.
2 Corinthians 5:21