The area of the theatre in which the performance takes place is referred to as the stage.
In order to keep track of how performers and set pieces move around the space, the stage is divided up into sections oriented based on the performers perspective to the audience.
Outside the theatre itself this includes the lobby, coat check, ticketing counters, and restrooms.
More specifically, the house refers to any area in the theatre where the audience is seated.
This can also include aisles, the orchestra pit, control booth, balconies and boxes.