The Apocrypha refers to books that were included in the Septuagint (the Greek version of the Hebrew scriptures created by Alexandrian Jews in the third century BCE) but excluded later by the rabbis who authorized the Jewish canon (about 100 CE). The contents of the Apocrypha are generally: Tobit, Judith, additions to the Book of Esther (in the Greek version of Esther), the Wisdom of Solomon, Ecclesiasticus (Wisdom of Jesus son of Sirach), Baruch, Letter of Jeremiah, Prayer of Azariah and the Son of the Three Jews, Susanna, Bel and the Dragon, 1 and 2 Maccabees, 1 and 2 Esdras, and the Prayer of Manasseh.
From the third century BCE through the end of the first century CE, the Septuagint was scripture for Greek-speaking Jews. From the 40s it was also scripture for Greek-speaking Christians, including Paul and the authors of the gospels, who quote from the Septuagint. From the latter part of the first century through the third century, the Septuagint was the scripture of the Greek-speaking churches. Early church fathers relied on the Septuagint and quoted passages, as scripture, from books in the Septuagint that were later classified as apocryphal.
When Jerome prepared the Latin Vulgate at the end of the fourth century, he followed the Hebrew canon for the Old Testament and used prefaces to distinguish the apocryphal books. As the Vulgate was copied over the centuries, these prefaces were not always included. During the medieval period the Western church generally regarded the books of the Apocrypha as part of scripture.
Protestant translators used the Hebrew canon for the Old Testament and argued that the books in the Septuagint but not in the Hebrew canon should not read as scripture. In reaction to Protestant criticism, the Catholic Council of Trent in 1546 decreed that the Old Testament included the Septuagint (except the Prayer of Manasseh and 1 and 2 Esdras). Contemporary Catholic scholarship identifies the books authorized by the Council of Trent as deuterocanonical, which means "later added to the canon."
Eastern Orthodox churches include the Septuagint in the Old Testament canon. The Holy Synod of the Greek Orthodox Church also includes 1 Esdras, Psalm 151, the Prayer of Manasseh, and 3 Maccabees, and gives 4 Maccabees in an appendix. Slavonic Bibles approved by the Russian Orthodox Church contain the deuterocanonical books and also 1 and 2 Esdras (called 2 and 3 Esdras), Psalm 151, and 3 Maccabees.
In the past two millennia the Christian Bible has included various books. Even as there is no singlenmanuscript that can be identified as the first Bible, there is no single collection of books that Christians agree on as scripture. The assertion by some Protestants that the Christian Bible is the inerrant word of God ignores these facts. Biblical inerrancy is a post-Reformation belief that some Protestants have promoted to resist Catholic claims of infallible papal authority.
For more details see: The New Oxford Annotated Bible with the Apocrypha.