This is the first time that the audience sees Elizabeth, although we already know some about her. We already know about John's affair, and that he has ended it. We assume that Elizabeth has knowledge of it, because of her dismissal of Abigail and the rumors circling about Abigail. We also know already that Elizabeth has suffered some sort of illness.
In this scene, Miller uses a minimal amount of words, but those words speak powerfully. The couple addresses mundane things, speaking in short, concise sentences with an understood tone of tension. The stage directions help us understand this as well. When they transition into more serious topics, they tread lightly at first, giving the audience the impression that both are trying to be sensitive. The simple statement by John Proctor, "I mean to please you Elizabeth," speaks volumes to the audience, because we want to believe him.
When the subject of Abigail and the trial comes up, the conversation escalates, and we see the nature of the tension in their relationship -- neither have fully forgiven John for his actions. This tension provides further conflict for the plot, and culminates in Act IV before resolution is found.