The theatre where audiences watched Shakespeare's company perform many of his plays was called the Globe, situated on the south side of London.
It is thought that the stage was several feet above the ground where the people who paid a penny stood, and that it extended into the audience from the backstage wall. This was a model for construction of the Adams Shakespearean Theatre at the Utah Shakespeare Festival (see photo), with the difference being that all the audience is seated and no one has to stand.
As you can see in the photo, there is a center section near the back which is somewhat inset from the outer stage; this is called the inner below and is the area of the stage where bedchambers and intimate scenes with only two people were staged, so that a curtain could be drawn in front of it, while another scene begins on the stage closer to the audience. At the back of the inner below is a space for a curtain.
Two columns support the second story of the inner below, providing a balcony called the above. You can see that there is space behind the balcony where actors can walk, and that is called the inner above.
The stage has four possible entrances on the main floor and three entrances on the second floor, so all the actors in a court scene could enter at the same time.
All the main architectural features in the photo are permanent; some plays add various kinds of staircases to get from the first level of the stage to the balcony, and some plays separate the balcony completely from the main floor, so that actors have to go up or down stairs which are hidden backstage.
Items which can change are the curtains or doors at the front of the inner below, which can be of several different colors and can be open or closed; the kinds of doors, which can be plain wood, decorated, or replaced with iron gates; and the various kinds of furniture which can be brought onto the stage.