At the time of Christ, two versions of the Old Testament (or Tanakh) were in circulation: a Hebrew version and a Greek version. The Greek version is known as the "Septuagint" (or "LXX" for short), after the legend that 72 translators working independently came up with identical Greek translations.
Several books appear in the Septuagint that do not appear in the Hebrew version, most of which were written during the "intertestamental period" between Nehemiah (c. 432 BC) and Christ (c. 5 BC). These books were regarded by Jewish sages as Sefarim hizonim, extraneous books, and were not part of the Hebrew canon. Collectively these writings are known to both Jews and Christians as the "Apocrypha." The books of the Apocrypha are:
Esdras
Tobit
Judith
additions to Esther
Wisdom of Solomon
Ecclesiasticus
Baruch
Song of the Three Children
Susanna
Bel and the Dragon
The Prayer of Manasseh
1 Maccabees
2 Maccabees
[u]The early Christians, most of whom spoke Greek, used the Septuagint, which included the Apocrypha. [/u]The Apocrypha continued in common use among Christians until the Reformation, when the Hebrew canon was chosen as the Protestant Old Testament. Catholic and Orthodox Churches continue to use the Septuagint. The Catholic Church officially declared its choice at both the Council of Trent (1546) and the First Vatican Council (1869-70).
The only theological significance of the acceptance or nonacceptance of the Apocrypha is that the Books of the Maccabees support prayer for the dead, which Protestants do not accept.