The entry hall in your apartment house is an example of a foyer.
The large open area in a theater before you go into the auditorium is an example of a foyer.
Origin of foyer
- French social center from Old French foier fireplace from Vulgar Latin focārium from Late Latin neuter of focārius of the hearth (unattested sense) from Latin focus fire
From American Heritage Dictionary of the English Language, 5th Edition