Staging
"Staging" refers to everything that helps create the look, sound, and feel of a play for the audience. This would include...
Scenery
The first thing the audience sees when the curtain opens is the stage set itself; this often sets the tone for the play. For example, in A Streetcar Named Desire, the audience sees a shabby building which once had grand pretensions, a small apartment, in which a bed, being out of place, is emphasized, and a light with a naked bulb (which Blanche later covers up, much as she covers up her past and disguises all harsh and unpleasant things). Thus, Williams is giving the audience clues to the themes of the play from the very first moment.
Props
"Properties" (props for short) are the items placed on the set or used by the actors. They, too, can serve a purpose beyond the practical. In Trying to Find Chinatown, for example, there are few props: just the violin, the open music case, and the piece of paper Benjamin is holding. This minimalism draws attention to the symbolism of the items: the violin represents Ronnie's desire to leave his identity behind, and the paper (NOT a map) represents Benjamin's desire to find his identity.
Costumes
Costumes often establish the historical setting, the social background of the character, and the character's qualities. For example, in A Streetcar Named Desire, Blanche's clothes do not fit the surroundings in which she finds herself: "She is daintily dressed in a white suit with a fluffy bodice, necklace and earrings of pearl, white gloves and hat, looking as if she were arriving at a summer tea or cocktail party in the garden district." Blanche, likewise, is out of place in these surroundings; Williams immediately lets us see a conflict which is acted out later on in the play.
Music
Music can help create a mood, or it can symbolize a memory of a previous time, as it often does in A Streetcar Named Desire, for example, when Blanche hears the "Varsouviana."
Sound Effects
These are any deliberately created noises, other than the actors' voices or the music. They, too, can have more import than the practical. In The Stronger, for example, Mrs. X. shoots a toy pistol at Miss Y. The "BANG" signals a dramatic turn in the conversation.When you are watching a play, of course, you will see or hear all of these things; when reading it, you will see, in the play, stage directions, instructions and descriptions that the playwright has written to help create the look and atmosphere he or she wants. Sometimes these stage directions are very simple; other times, as in Tennessee Williams, for example, they are elaborate and detailed, and help establish the themes and symbols of the play.