The Old Testament consists with all of the events that happened before Jesus was born. The New Testament consists with all of the events that happened after Jesus was born.
People experienced God over a long period of time. People shared their stories of their experiences of God orally. The leaders of the church determined the official collection of inspired books that is the Bible. People speaking different languages translated the Bible into their own languages from the Bible's original languages which are Hebrew, Aramaic, and Greek.
Early Christians were especially concerned about protecting and safeguarding the message of Jesus Christ by writing it down so it would never be forgotten.
The Four Commonly used Catholic Bible English translations were the Authorized King James Version, Revised Version, Revised Standard Version, and the New Revised Standard Version.