The ark is known in Hebrew as the aron kodesh or aron ha-kodesh ("holy ark") by the Ashkenazim and as the heikhal ("sanctuary") among Sefardim. Aron kodesh comes from Hebrew אָרוֹן קׄדֶש ʼārōn qōdeš (i.e. aron kodesh), Holy Ark. This name is a reference to the ’ārōn haqqōdeš, the Hebrew name for the Ark of the Covenant which was stored in the Holy of Holies in the inner sanctuary of both the ancient Tabernacle and the Temple in Jerusalem. Similarly, Hekhál, also written hechal, echal or heichal — and sometimes also Echal Kodesh (mainly among Balkan Sephardim) comes from Hebrew הֵיכָל [hēkhāl] ‘palace’, was used in the same time period to refer to the inner sanctuary. The hekhal contained the Menorah, Altar of Incense, and Table of the Showbread.
Most arks feature a parokhet (curtain) placed either outside the doors of the holy ark (Ashkenazi and Mizrachi custom) or inside the doors of the ark (Spanish and Portuguese and Moroccan Sephardi custom).
The ark is often placed on the wall of the sanctuary which is facing Jerusalem, though it is sometimes placed on the north wall or another wall for architectural reasons. In those cases where the ark does not show the direction to Jerusalem, traditional Judaism instructs the worshiper to face the true direction towards Jerusalem in prayers such as the Amidah.
In some ancient synagogues, such as the fifth-century synagogue in Susia, the Torah scroll was not placed inside the synagogue at all, but in a room adjacent to it, signifying that the sacredness of the synagogue does not come from the ark but from its being a house of prayer. The Torah was brought into the synagogue for reading purposes.