An orchestra pit is the space where an orchestra plays in a theatre or opera house. The actors or singers are on the stage, and the orchestra pit is normally lower than the stage so that the audience can watch the play or opera. Depending on where they sit, the audience may just be able to see the heads of the musicians in the orchestra pit. It is important that singers can see the conductor so that they can watch the beat out of the corner of their eye. Opera houses nowadays often have close-circuit television monitors at the sides so that singers can watch the conductor even when they are not facing him.
The orchestra pit in the Bayreuth Festspielhaus is unusual. This opera house was designed by the composer Richard Wagner for the performance of his own operas. He did not want the audience to be able to see the orchestra at all, so it is very low. The orchestra members do not have to dress up in ties and jackets because they cannot be seen anyway.