In the world of the theatre, to take a box was to show that one was privileged. It was expensive and only seated a few people. Sometimes, as in this painting, it was reserved for just two people. A further privilege was to be able to withdraw to the back of the box where they had complete privacy; or to sit at the front and see and be seen by the audience.
In this painting Renoir portrays a man and a woman sitting in their box. The young woman sits in front with her hand, in which she is holding her opera glasses, resting on the plush covered ledge at the front of the box. She is looking out at the viewer of the painting, not down at the stage. Her escort is a bearded gentleman in full evening dress sitting further back in the shadows.