1.Othello’s private life, where his marriage is soon to become public knowledge, where Brabantio threatens Othello with violence and accuses him of using sorcery to seduce Desdemona, his reasoning being that she would never marry Othello voluntarily. Second,  the political crisis with the threatened attack by the Turks, where he anticipates being sent to war in a commanding position.

2. When Iago says “I am not what I am,” he means that he is not truly and in essence what he merely pretends to be. He pretends to be a servant of Othello, but he is really a servant of himself.

3. Brabantio say to Othello: 

“She has deceived her father, and may thee” [line 650] because he wants to unsettle the relationship between Desdemona  and Othello, so they don’t stay together. What he meant by this is that she betrayed her  own father and married an african man against his will, she can betray you the same way.

4. Iago wants to lead Cassio into committing an action that will disgrace him with the other soldiers.

5. This little piece of cloth became very important. Othello had originally given the handkerchief to Desdemona. Iago convinces Othello that Cassio gave it to Bianca, which convinces him that Cassio and Desdemona are having an affair. When the handkerchief’s role in things is revealed in the final act, Emilia realizes all the manipulation Iago’s done, and what a monster she’s married to.