At its heart, Salvation is the process of becoming a child of God.
When a mother gives life to her son, the child receives the very human nature - the DNA - of his mother. The child possesses the very nature of his mother and father, bringing about a real likeness to his parents.
In the beginning of humanity's existence, God created man and woman to share in his supernatural divine life as his very own children. This is a supernatural gift above and beyond our natural humanity, and it elevates our humanity with the divinity of our Creator.
In the Book of Genesis, this absolutely incredible and supernatural gift is told through the following poetic imagery:
"The LORD God formed man of dust from the ground, and breathed into his nostrils the breath of life and man became a living being." (Genesis 2:7)
It was only upon humanity that God breathed this extra gift of life. Earlier in Genesis, the beasts, the fish, the birds... these were created and are alive, but they didn't receive God's "breath of life."
In in the Hebrew, the term for "breath of life" is ruah, which is the same word used for the very spirit of God.
This breath of life made our first parents the very children of God, sharing in God's divine life!
Another way the Book of Genesis relates this divine sonship is by saying that our first parents were created in the image and likeness of God.
The Original Sin
The Book of Genesis then describes a very real event that occurred near the beginning of humanity's advent, by means of poetic imagery: This supernatural gift of divine sonship was lost by our first parents, through the first sin. We call this Original Sin.
Original Sin is not only the first sin that was committed, but it is also a term that describes the ongoing privation - the lack of - God's divine life in the human soul and body. It is the loss of divine sonship or divine filiation. After the first sin, we remain God's beloved creatures, but we have wandered outside of God's divine life.
We see the effects of Original Sin in our daily lives. We suffer. We die. We have disordered desires. We have darkened intellects. We have weakened wills. We are sinners at war with ourselves internally, with one another in our relationships, and with God through our continual disobedience and lack of trust in him.
If left untreated, this sad state will result in eternal separation from God through the state we call Hell. Hell is essentially eternal separation from God: the lack or privation of his life for all eternity.
The Good News
After carefully preparing humanity for centuries, God delightfully surprised us by becoming one of us. He assumed our humanity, infusing his divinity with our humanity through the incarnation of Jesus in the womb of Mary.
The eternal Son of God became one of us so we can become children of God through him!
Jesus ultimately made this reunification with God - becoming God's children - possible through his redeeming work: his intense suffering, death, and resurrection from the dead. These salvific acts were imbued with his divine love, offered on our behalf, to atone for our sins.
When we are united back to God through Jesus' death and resurrection in baptism, we are reborn as children of God... and given the ability to live a life of faithfulness by the power of the Holy Spirit!
This event of being born from above, by means of the spirit, in baptism, is also called initial justification. It is the glorious event of our salvation... our spiritual rising from the dead... our being made children of God through the power of God's free gift of grace.
After our baptism, we grow in our divine sonship through the process of becoming holy. Another term for this is sanctification or ongoing justification. By growing in the life of Jesus, we become more and more configured and conformed to the divine image of God. Essentially, we experience growth as God's children, becoming more and more like Jesus.
After Baptism, we can reject God's good gift of his divine life.
Through serious sin committed intentionally, we can commit sin that is called mortal.
This is sin that deprives us of God's life once again, returning us to our former status of waywardness.
The Good News is that Jesus gave his apostles, and their successors, the ability to forgive sins, by breathing his spirit upon them:
Jesus said to them again, "Peace be with you. As the Father has sent me, even so I send you."
And when he had said this, he breathed on them, and said to them, "Receive the Holy Spirit.
If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained."
Since this incredible gift was given to the ministers of Christ's Church, we have the awesome gift of the Sacrament of Confession whereby validly ordained ministers are able to forgive the sins of Christians, bringing them back into the life of divine sonship by the power of the Holy Spirit, the very breath of God.
By means of these two incredibly powerful sacraments - Baptism and Confession - God restores us to his divine life, raising us from spiritual death, and uniting us to his divine family, which is the Church.
In the Family of God, we receive older brothers and sisters, whom we call the saints. God becomes our Father (Romans 8:15). Mary becomes our spiritual mother (John 19:26-27), and we learn the discipline of God (Hebrews 12:7), which leads us along the path to eternal joy in Heaven!