wikipedia | A tabernacle is the fixed, locked box in which, in some Christian churches, the Eucharist is "reserved" (stored). A less obvious container, set into the wall, is called an aumbry.
Within Catholicism, Eastern Orthodoxy and in some congregations of Anglicanism and Lutheranism, a tabernacle is a box-like vessel for the exclusive reservation of the consecrated Eucharist. It is normally made of metal, stone or wood, is lockable and secured to its altar to prevent the consecrated elements within from being removed without authorization. The "reserved Eucharist" is secured there for distribution at services, for availability to bring Holy Communion to the sick, and, especially in the Western Church, as the center of attention for meditation and prayer. The term "tabernacle" arose for this item as a reference to the Old Testament tabernacle which was the locus of God's presence among the Jewish people - hence, it was formerly required (and is still generally customary) that the tabernacle be covered with a tent-like veil or curtains across its door when the Eucharist is present within.