The Canon of Scripture

Old and New Testaments make the Bible

The apostolic Tradition that the Church decided to continue in the teachings is composed of the canon of Scripture, the Old and New Testaments.
The Old Testament has never been revoked and it holds truth as the Old Covenant. It prepares us for the coming of Christ, "redeemer of all men." 

The divine teachings of God are revealed through "sound wisdom of human life.. wonderful treasury of prayers, and the mystery of our salvation is present in a hidden way." The Word of God is not to be rejected by the church.
The New Testament is also the Word of God, but here He brings salvation to everyone who has faith. 

It central concentrates in Jesus Christ, "God's incarnate Son: his acts, teachings, Passion, and glorification, and his Church's beginnings under the Spirit's guidance."

The heart of all scriptures is the Gospels since they are the source of life and Incarnate word of Jesus our Savior.
The Stages of formation are:
1. The life and teachings of Jesus.
2. The oral tradition.3. The written Gospels.

The unity of the Old and New testaments were placed together by the divine illumination and plan through typology, which "discerns in God's works of the Old Covenant prefigurations of what he accomplished in the fullness of time in the person of his incarnate Son.

The Old testament retains its own intrinsic values as we read about the light of Christ crucified and risen. Revelation reaffirms by the Lord himself that he does. The New testament must be read in the light of the Old, but also we can see how the Old is unveiled.

Typology indicates the "dynamic movement toward the fulfillment of the divine plan when "God (will) be everything for everyone."

Source: 

Catechism of the Catholic Church.

Catechism of the Catholic Church. New York: Doubleday, 1995. Print. 

Part One: The Profession of Faith

Section One: "I Believe" - "We Believe"

Chapter Two: God Comes to Meet Man

Article 3: Sacred Scripture

IV. The Canon of Scripture (40-42)