What is the name of the ground level of a theatre where spectators watch performances?

Parterre isn't in common use here. I know that area mainly as "the stalls", whereas "the pit" is the lower bit at the front for the orchestra, i.e. "the orchestra pit

Very interesting; we’ve always called the ground floor seating the “Orchestra” and the “Pit” is where the orchestra actually sits and performs for stage plays and musicals, Broadway, etc.

I was looking for the main floor for audience seating. The pit is for the orchestra.

I was looking for the option "stalls" never heard of Parterre before!!