https://en.wikipedia.org/wiki/Church_tabernacle

A tabernacle is a fixed, locked box in which, in some Christian churches, the Eucharist is "reserved" (stored). A less obvious container for the same purpose, set into a 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 or adjacent wall 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.

https://en.wikipedia.org/wiki/Reserved_sacrament

In many Christian churches some portion of the consecrated elements is set aside and reserved after the reception of the Holy Eucharist, referred to as the reserved sacrament. The reserved sacrament is usually stored in a tabernacle, a locked cabinet made of precious materials and usually located on, above or near the high altar. In Western Christianity usually only the Host, from Latin: hostia, meaning "victim" (the consecrated bread), is reserved.