What parts did the Greek theater building have?

To reduce the cost of building a theater, the ancient Greeks usually built it at the foot of a mountain or hill. The theater building consisted of the following parts:
1) a theater-square for spectators, which was built in the form of tiers, which rose from the center of the building in the form of a semicircle;
2) skene-place where the actors’ belongings were kept;
3) orchestra – a flat platform for the choir and actors;
4) scene-quadrangular square behind the orchestra.