In Christian churches there are many holy things, sacred vessels. The tabernacle is one of the main shrines of an Orthodox church, to which only clergy have the right to touch.
The tabernacle is a sacred vessel containing the main shrine of the Orthodox Church - the Body and Blood of the Lord Jesus Christ. Otherwise, the Body and Blood of the Savior are called holy gifts - hence the name of the sacred vessel in which the shrine is located.
Usually tabernacles are made in the form of a small temple, inside which is a reliquary with dried holy gifts. These holy gifts are used for the communion of sick people at home. The Body and Blood are prepared in advance at the liturgies during Great Lent and then kept in the tabernacle for the whole year.
Tabernacles are in the altar of an Orthodox church on the holy throne. This vessel is covered with a glass cover on top. The sizes of tabernacles are different - it all depends on the size of the most holy altar of the temple.
Also tabernacles can be called Zion or Jerusalem. This name is due to the appearance - these tabernacles are a kind of architecture of the Jerusalem temple. Historically, such tabernacles were carried out of the altar by a deacon at a certain point in the service.
It is worth noting that tabernacles are used not only in Orthodoxy, but also in Catholicism and Anglicanism.