“The Apocrypha” names a group of Jewish writings composed in the Second Temple period — roughly the third century BCE through the first century CE — that the Greek Septuagint includes but the Hebrew Bible (as canonized by Jewish tradition) does not. The Roman Catholic and Eastern Orthodox churches receive these books as canonical (Catholics typically call them deuterocanonical). Most Protestant Bibles set them apart or omit them; the Latter-day Saint canon does not include them.
The collection contains substantial works of several kinds. The historical narratives include Tobit, Judith, and 1 and 2 Maccabees (the latter the standard ancient source on the Maccabean revolt and the rededication of the temple, the historical setting of Hanukkah). The wisdom books include the Wisdom of Solomon and the Wisdom of Sirach (also called Ecclesiasticus) — both substantial works of Jewish wisdom literature. Baruch is a prophetic work attributed to Jeremiah’s scribe. There are also additions to canonical books: extra Greek chapters added to Esther and Daniel (including the stories of Susanna and of Bel and the Dragon).
Doctrine and Covenants 91 speaks directly to the Apocrypha. In March 1833, Joseph Smith asked the Lord whether he should include the Apocrypha in his revision of the Bible. The Lord’s answer:
There are many things contained therein that are true, and it is mostly translated correctly; there are many things contained therein that are not true, which are interpolations by the hands of men. … whoso readeth it, let him understand, for the Spirit manifesteth truth.
The Apocrypha is therefore neither dismissed nor canonized in the Latter-day Saint tradition; it is a body of writings the faithful reader can profit from when read in the Spirit. The works are also significant for the contextual background they give the New Testament — Hellenistic Judaism, the Maccabean wars, and the wisdom-and-piety traditions in which Jesus’s first hearers lived.