It is the oldest of several ancient translations of the Hebrew Bible into Greek, lingua franca of the eastern Mediterranean Basin from the time of Alexander the Great (356-323 BCE).

The Septuagint was held in great respect in ancient times; Philo and Josephus ascribed divine inspiration to its authors.^[4] Besides the Old Latin versions, the LXX is also the basis for the Slavonic, the Syriac, Old Armenian, Old Georgian and Coptic versions of the Old Testament.^[5] Of significance for all Christians and for Bible scholars, the LXX is quoted by the New Testament and by the Apostolic Fathers.

Jewish scholars first translated the Torah into Koine Greek in the 3rd century BCE.^[6][7] According to the record in the Talmud,

'King Ptolemy once gathered 72 Elders. He placed them in 72 chambers, each of them in a separate one, without revealing to them why they were summoned. He entered each one's room and said: "Write for me the Torah of Moshe, your teacher." God put it in the heart of each one to translate identically as all the others did.'^[8]

Further books were translated over the next two centuries. It is not altogether clear which was translated when, or where; some may even have been translated twice, into different versions, and then revised.^[9]

The quality and style of the different translators also varied considerably from book to book, from the literal to paraphrasing to interpretative.

As the work of translation progressed gradually, and new books were added to the collection, the compass of the Greek Bible came to be somewhat indefinite. The Pentateuch always maintained its pre-eminence as the basis of the canon; but the prophetic collection (out of which the Nevi'im were selected) changed its aspect by having various hagiographa incorporated into it.

Some of the newer works, those called anagignoskomena in Greek, are not included in the Jewish canon. Among these books are Maccabees and the Wisdom of Ben Sira. Also, the Septuagint version of some works, like Daniel and Esther, are longer than those in the Masoretic Text.^[10] Some of the later books (Wisdom of Solomon, 2 Maccabees, and others) apparently were not translated, but composed in Greek.

The authority of the larger group of "writings", out of which the ketuvim were selected, had not yet been determined, although some sort of selective process must have been employed because the Septuagint did not include other well-known Jewish documents such as Enoch or Jubilees or other writings that are now part of the Pseudepigrapha. It is not known what principles were used to determine the contents of the Septuagint beyond the "Law and the Prophets", a phrase used several times in the New Testament.

From http://en.wikipedia.org/wiki/Masoretic_Text  (part of their article)

The Masoretic Text (MT, ��, or ) is the authoritative Hebrew text of the Jewish Bible regarded almost universally as the official version of the Tanakh.^{[citation needed]} It defines not just the books of the Jewish canon, but also the precise letter-text of the biblical books in Judaism, as well as their vocalization and accentuation known as the Masorah.

The MT is also widely used as the basis for translations of the Old Testament in Protestant Bibles, and in recent years (since 1943) also for some Catholic Bibles.^[1] In modern times the Dead Sea Scrolls have shown the MT to be nearly identical to some texts of the Tanakh dating from 200 BCE but different from others.

The MT was primarily copied, edited and distributed by a group of Jews known as the Masoretes between the 7th and 10th centuries CE. Though the consonants differ little from the text generally accepted in the early 2nd century (and also differ little from some Qumran texts that are even older), it has numerous differences of both greater and lesser significance when compared to (extant 4th century) manuscripts of the Septuagint, a Greek translation (made in the 3rd to 2nd centuries BCE) of the Hebrew Scriptures that was in popular use in Egypt and Palestine and that is believed by scholars^[2] to be the source often quoted in the New Testament.

The Hebrew word mesorah (מסורה, alt. מסורת) refers to the transmission of a tradition. In a very broad sense it can refer to the entire chain of Jewish tradition (see Oral law), but in reference to the Masoretic Text the word mesorah has a very specific meaning: the diacritic markings of the text of the Hebrew Bible and concise marginal notes in manuscripts (and later printings) of the Hebrew Bible which note textual details, usually about the precise spelling of words.

The oldest extant manuscripts of the Masoretic Text date from approximately the 9th century AD,^[3] and the Aleppo Codex (once the oldest complete copy of the Masoretic Text, but now missing its Torah section) dates from the 10th century.

The Talmud (and also Karaite mss.) states that a standard copy of the Hebrew Bible was kept in the court of the Temple in Jerusalem for the benefit of copyists; there were paid correctors of Biblical books among the officers of the Temple (Talmud, tractate Ketubot 106a).

This copy is mentioned in the Aristeas Letter (§ 30; comp. Blau, Studien zum Althebr. Buchwesen, p. 100); in the statements of Philo (preamble to his "Analysis of the Political Constitution of the Jews") and in Josephus (Contra Ap. i. 8).

Another Talmudic story, perhaps referring to an earlier time, relates that three Torah scrolls were found in the Temple court but were at variance with each other. The differences were then resolved by majority decision among the three.