Narthex

Nartex of a Patriarchate Monastery in Serbia

The narthex of a church is the entrance or lobby area, located at the end of the nave, at the far end from 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 was either an indoor area separated from the nave by a screen or rail, or an external structure such as a porch.
Narthex works like a filter, allowing those not eligible for admittance into the general congregation to hear and partake in the service.