From HistoryWiki

Narthex Soundex Code C620

Wikipedia page about Narthex

The Narthex is an architectural element typical of early Christian and Byzantine basilicas or churches consisting of the entrance or lobby area, usually located at the west end of the nave, opposite the church's main altar. Traditionally the Narthex was a part of the church building, but was not considered part of the church proper. It is either an indoor area separated from the nave by a screen or rail, or an external structure such as a porch.

By extension, it can also denote a covered porch or entrance to a building.