It can be difficult to understand all the different words associated with salvation. That said, here is an overview and a list of definitions to make it easier.
Overview
God calls us to be His children.
When we sinned, we dishonored God, brought about His justice, and lost our chance to be His children.
But God sent His only Son, Jesus Christ, to pay the price for our sins so that God’s honor would be repaired, God’s justice would be appeased and God’s Divine Adoption of us, his children, would be restored.
This price is called Redemption.
Christ’s Redemption was the painful work of His daily labours, sufferings and death that He did to restore our relationship with God (this restoration of our relationship is called Reconciliation).
The part of Redemption that repaired God’s honor and appeased His justice is called Satisfaction.
The part of Redemption that restored our Divine Adoption is called Atonement.
Now, God gives us help to respond to His initial call to be His children (this help is called Grace).
Grace causes us to turn away from sin and towards God (this turning away is called Conversion).
Due to Conversion, God erases our sins against Him (this erasure of our sins is called Forgiveness) and begins the process of changing us into His children (this process is called Justification).
Justification begins with God canceling the punishment for our sins (this cancellation is called the Remission of Sins). Because of God’s Forgiveness and the Remission of our Sins, we are now free from sin and its consequences (this freedom is called Salvation).
Then, through Justification, God cleanses our hearts so that we lose the inclination to sin and instead apply ourselves towards God (this cleansing of our hearts is called Purification and this application of ourselves towards God is called Holiness).
With Justification, God claims us as His own (this justification and God’s claiming us as His own is called Sanctification).
As a result of Justification, we begin doing the right things influenced by God’s love (this doing of the right things is called Righteousness).
Definitions
Grace
God calls us to be with Him as His children. Grace is God’s help given to us by the Holy Spirit to respond to that call (CCC 1996).
Conversion
The first thing grace does for us is conversion. Conversion is us turning away from sin and towards God. By conversion, we are justified, and we accept God’s forgiveness and righteousness. (CCC 1989)
Justification
Justification is a process following conversion and Baptism where our sins are remitted, our hearts are purified from sin, and we are sanctified. (CCC 1987-1995) Justification is also where we go from being children of Adam to children of God.1
Remission of Sins
When we sin, there is a punishment we must undergo. The remission of sins means that this punishment is cancelled (CCC 1471).
Purification
Purification is an act of God where He cleanses our souls of all inclinations towards sin so that we achieve the holiness necessary to see God in Heaven (CCC 1030).
Holiness
(aka Sanctity)
Holiness is a virtue where we apply our mind and our actions towards God.2
Sanctification
Sanctification is an act of God where He justifies us and claims us as His own.2
Forgiveness
An act of God where He “effaces” (completely erases) away our offenses against Him and we receive the grace of justification (CCC 987).
Righteousness
A state gifted to us by God as a result of Justification where we do the right things influenced by God’s love (CCC 1991).
Salvation
A state gifted to us by God where we are freed from sin and its consequences.3
Reconciliation
When we sin, we break up our relationship with God and with the Church. Reconciliation is when our relationship with God and with the Church is re-established.4
Redemption
Redemption is the price Christ paid on our behalf to to repair God’s honor and appease God’s justice; and the price necessary to restore us to being children of God, an ongoing process until our salvation. That price He paid for us was His death on the Cross.5
Atonement
Atonement refers to the painful work Christ did to reconcile us to God. When we sinned, we lost Divine Adoption, the state of being children of God. Christ, by His works, sufferings and death, made complete atonement for our sins and reconciled us to God.6
Satisfaction
Satisfaction refers to the painful work Christ did to fully repair the honor of God. When we sinned, we dishonored God. Christ, by His works, sufferings and death, made complete satisfaction for our sins and restored the honor of God.5