With respect to sacred Scripture, the Apocrypha are those religious books written in the Old and New Testaments eras that claimed a sacred origin but were ultimately judged by the Catholic Church as not inspired by the Holy Spirit. These apocryphal books were thus excluded from the canon of Scripture, and yet in many cases retain some religious value.
Our Protestant brothers and sisters mistakenly place the deuterocanonicals (seven Old Testament books) in this category. For more on the deuterocanonicals, see this article and this article from Catholic Answers Magazine. In addition, for more on the apocryphal books, see this article from The Catholic Encyclopedia.