"the seeing place"
It is between the two entrances of the chorus, or the parados. It is in the middle of the theatre.
"where the action occurs"
This is where the play takes place. It is located in front of the theatron and the parados. It holds the thymele.
"the altar to Dionysus"
Since Dionysus was the Greek God of Theatre, there is an altar dedicated to him. The thymele is located within the orchestra.
"the dressing room"
It is located behind the orchestra, the thymele, and the proskerion. It is behind all of these since it is a dressing room.
"the backdrop for scenery"
Any backdrops used in the play will be seen here, located behind the orchestra and the thymele. It provides visual aids to setting.