Why were some books included in the Bible and not others?

The process of deciding what was 'Scripture' took a long time. 'Scripture' is the Jewish and Christian name for writings that are considered to be holy and spoken by God. In the centuries before Christ, religious Jews used the books that we now call the Old Testament for teaching and instructing the people, as well as warning them and having worship services. Then in the time after Christ came, those who followed him also used the Old Testament but wrote their own books that were about Christ's life. Those that were considered to have special authority because of their power during use in teaching and their connection to eyewitnesses of Jesus Christ were included in the Bible, called 'the canon'.