An 'Aside' occurs when a speaker on stage mumbles words intended for the audience only.
In a play, an "Aside" is a moment when a character speaks directly to the audience, but the other characters on stage do not hear what is being said. The words spoken during an Aside are usually a character's inner thoughts, feelings or intentions that they do not want other characters to hear. It is like the character is breaking the fourth wall and speaking directly to the audience. As the other characters on stage are not aware of the aside, it is intended only for the audience to hear and understand what is happening in the character's mind.