Q. 1. What is the purpose of the ambry?

A. 1. The traditional purpose of the ambry (or almery, aumbry; from the medieval form almarium, cf. Lat. armarium, "a place for keeping tools", French = armoire) was a recessed cabinet in the wall of the Catholic church for storing Sacred vessels and vestments.

Nowadays, ambries are used to house the oil for the Anointing of the Sick.

Traditionally, the ambry if located in the sanctuary (as in, the altar area) of a church or in the Baptistery, and is used to store the oils used in the Sacraments: the Oil of catechumens (indicated by the Latin letters O.C.), the Oil of the Sick (O.I.), and he Sacred Chrism (S.C.). Former regulations required it to be secured and locked, and lined and veiled with either purple cloth (in reference to the Oil of the Sick) or white (for the Sacred Chrism). The door was usually marked "O.S." or Olea Sancta, to indicate the contents. Such regulations are now relaxed so that while many churches continue to use such an ambry, the oils are also stored and in some cases displayed in other ways.

[Source: https://en.wikipedia.org/wiki/Ambry]