In the beginning of Act 4, scene 1, Shakespeare uses word choice or diction to develop Othello's inner conflict. Iago uses language about what Cassio could be doing with Desdemona. he uses the words "naked" and "unauthorized kiss" to make Othello jump to conclusions. He futher uses the word "lie" to make Othello think about Cassio having sex with Desdemona. Iago even saysWith her, on her, what you will.
meaning that Othello can take the words however he wants.
Later Shakespeare uses stage directions and action to demonstrate Othello's conflict externally: Othello passes out. This demonstrates how the news affects him not only emotionally, but physically.
While out, Iago's asides to the audience reveal that he plans to manipulate Othello further with words.
Iago tells Othello to hide while he talks to Cassio about his woman. But his woman is Bianca, and Othello is led to believe that this woman they discuss is Desdemona. When we as the audience know something that characters don't know that is called dramatic irony. While the audience watches Iago and Cassio talk about Bianca, Cassio speaks with great confidence about how this woman adores him. Othello is hiding and overhears all of these words. We get to hear Othello's thoughts and we know he is misinterpreting what Cassio is saying.
Character relationships are particularly important in this scene because everyone seems to trust Iago, yet he proves to the audience time and again that he is not trustworthy.
This discussion further contributes to Othello's external conflict with his wife, and it further complicates his own inner struggle with himself and his self confidence.