Act 1 of Shakespeare's The Winter's Tale, like the first act of all of Shakespeare's plays as well as the first act of most plays ever written, provides much of the exposition of the play.
Exposition is what the audience learns about the setting of the play, the major characters in the play, the nature of the underlying conflict of the play, important events which occurred prior to the play which have an effect on the play, and anything else that the playwright thinks the audience needs to know to be able to follow and understand the action of the play.
Exposition can also be used to reveal characters' motivations for what they do during the play, to present the themes of the play, and to foreshadow events that have yet to occur in the play.
Exposition can take the form of narration, such as that which is made by the Chorus in the prologue of Romeo and Juliet or Henry V, dialogue, narrative dialogue, messengers, letters, or any other forms in which the information can be presented.
In act 1, scene 1 of The Winter's Tale, the exposition is presented by narrative dialogue. The play opens with a conversation between Camillo, Leontes's Lord Chamberlain, and Archidamus, a Bohemian lord. This scene has no dramatic significance in the play. The purpose of the scene is to show the relationship between these two characters, to show their relationship to other characters who will be introduced later in the play, and to provide background information.
In this fairly short scene, Camillo and Archidamus talk about the good relationship of their respective kings, Leontes of Sicilia and Polixenes of Bohemia, and about Mamillius, the young prince of Sicilia.
In act 1, scene 2, the exposition continues, this time with more substantive dialogue.
The two kings, Leontes and Polixenes, appear in this scene, as does the young prince Mamillius, Leontes's pregnant queen, Hermione, and Camillo.
The audience learns more about these characters and their relationships to each other. Shakespeare lays the groundwork for Leontes's jealousy of Polixenes and Hermione with Leontes's asides to the audience.
Leontes's jealousy rises to the point that he asks Camillo to poison Polixenes. Camillo agrees, if unwillingly, simply because he sees no point in arguing with Leontes about it. Leontes exits, believing that his plot to poison Polixenes is going forward.
Polixenes reenters the scene, and Camillo confides in him that Leontes believes that Hermione has been unfaithful to him with Polixenes and that he ordered Camillo to poison Polixenes.
Camillo suggests that Polixenes leave Sicilia as soon as possible and that Camillo go with him, so Camillo can avoid Leontes's threat to have him executed if he fails to poison Polixenes.
With these elements of the exposition of the play firmly established in these two scenes, the play moves forward.