In a play, if a character is 'breaking the fourth wall', who are they talking to?

The fourth wall is a performance convention in which an invisible, imagined wall separates actors from the audience. While the audience can see through this "wall", the convention assumes, the actors act as if they cannot. From the 16th century onwards, the rise of illusionism in staging practices, which culminated in the realism and naturalism of the theatre of the 19th century, led to the development of the fourth wall concept.

"Breaking the fourth wall" is any instance in which this performance convention, having been adopted more generally in the drama, is violated. This can be done through either directly referencing the audience, the play as a play, or the characters' fictionality. The temporary suspension of the convention in this way draws attention to its use in the rest of the performance. This act of drawing attention to a play's performance conventions is metatheatrical.