The Biblical canon is the officially recognized list of books which are considered part of the Bible. The first Christians used the Greek translation of the Old Testament known as the Septuagint which was written and read by Jews as the Greek language had generally replaced Hebrew. In the Council of Jamnia of 90 A.D., Jewish rabbis rejected the Septuagint in favor of the Hebrew language text, and omitted certain books such as Baruch, Judith, Maccabees, Sirach, and Tobit, relatively recent contributions which had become part of Jewish culture.
The Eastern Christian churches continue to use the Greek Septuagint to this day, but the Western Church of Catholicism commissioned a Latin translation from Saint Jerome in the early 5th century which came to be known as the Vulgate. It remains the official Roman Catholic Bible.
The Biblical New Testament was taking shape by the end of the first century when the Gospels and the letters of Paul were already being circulated. The heretic Marcion attempted to remove some books around 140 A.D., showing that there was already a grouping of books that were accepted as authentic. Twenty of the 27 books of the New Testament were accepted early in the history of Christianity, while the other seven that make up the Scriptures had a longer ride. When Constantine first made Christianity a legal religion in the Roman Empire in the early 300s, he called together leading Christians from the East and West parts of the empire to iron out the principles of Christianity, including cementing the canon. Subsequent councils dealt with minor questions of authenticity. For the Catholic Church, they made a formal proclamation at the Council of Trent, that the Bible they had been using and the books it contained were correct, in reaction to the Protestant Reformation's rejection of the deuterocanonical works as apocryphal. The 1611 King James Bible, put together after the Church of England had broken away from the Catholic Church under Henry VIII, included these books but placed them in a separate section, and the Church of England continued to use the deuterocanonicals in the liturgy until forbidden by the Long Parliament in 1644. By the 1800s Protestant Bibles began to omit the deuterocanonical books altogether.
Orthodox Christians do not usually speak of "the canon of Scripture" but do think of the writings as "canonical", the difference being that the canonical writings are judged as being faithful to the dogma of the Church. The Orthodox Church has never defined the Old Testament canon, but they have been using the same one since the early times of the Church.