The Apocryphya are the Deuterocanonical books which were removed from the King James Bible. Protestant Bibles have only 39 books in the Old Testament, however, while Catholic Bibles have 46. The seven additional books included in Catholic Bibles are Tobit, Judith, 1 and 2 Maccabees, Wisdom, Sirach, and Baruch. Catholic Bibles also include additions to the Books of Esther and Daniel which are not found in Protestant Bibles. These books are called the deuterocanonical books. The Catholic Church considers these books to be inspired by the Holy Spirit.
Protestants attempt to defend their rejection of the deuterocanonicals on the ground that the early Jews rejected them. However, the Jewish councils that rejected them (e.g., School of Javneh (also called “Jamnia” in 90 - 100 A.D.) were the same councils that rejected the entire New Testatment canon. Thus, those who reject the Catholic Bible are following a Jewish council that rejected Christ and the Revelation of the New Testament.
This explanation is incomplete. The definition of “apocrypha” depends on who is doing the defining. For Catholics, “apocrypha” would consist of those books not found in the 73-book Bible. The seven Deuterocanonical books are NOT apocryphal to Catholics. For many Protestants, however, their “apocrypha” consist of any books not found in their 66-book Bible, including the Deuterocanonicals.
So, for Catholics, apocryphal works are such things as the Gospel of James, the Gospel of Thomas, etc. For Protestants, their apocrypha would include those things and also (for many Protstants, anyway) the deuteros.
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