Aperance

Appearance and reality are important aspects in Othello. For Othello, seeing is believing, and proof of the truth is visual. To "prove" something is to investigate it to the point where its true nature is revealed. Othello demands of Iago "Villain, be sure thou prove my love a whore, be sure of it, give me the ocular proof" (Act 3, Scene 3).
What Iago gives him instead is imaginary pictures of Cassio and Desdemona to feed his jealousy. As Othello loses control of his mind, these pictures dominate his thoughts. He looks at Desdemona's whiteness and is swept up in the traditional symbolism of white for purity and black for evil. Whenever he is in doubt, that symbolism returns to haunt him and despite his experience, he cannot help but believe it.
Jealousy
Jealousy is what appears to destroy Othello. It is the emotion suggested to him by Iago in Act 3, Scene 3. Iago thinks he knows jealousy, having rehearsed it in his relationship with Emilia to the extent that Emilia believes jealousy is part of the personality of men, but Iago's jealously is a poor, weak thought compared to the storm of jealousy he stirs up in Othello.
Iago has noticed Othello's tendency to insecurity and overreaction, but not even Iago imagined Othello would go as far into jealousy as he did. Jealousy forces Othello's mind so tightly on one idea, the idea that Desdemona has betrayed him with Cassio, that no other assurance or explanation can penetrate. Such an obsession eclipses Othello's reason, his common sense, and his respect for justice.
Up to the moment he kills Desdemona, Othello's growing jealousy maddens him past the recall of reason. Upon seeing that she was innocent and that he killed her unjustly, Othello recovers. He can again see his life in proportion and grieve at the terrible thing he has done. Once again, he speaks with calm rationality, judging and condemning and finally executing himself.
Prejudice
Iago's scheme would not have worked without the underlying atmosphere of racial prejudice in Venetian society, a prejudice of which both Desdemona and Othello are very aware. Shakespeare's Desdemona copes with prejudice by denying it access to her own life. Her relationship with Othello is one of love, and she is deliberately loyal only to her marriage. Othello, however, is not aware how deeply prejudice has penetrated into his own personality. This absorbed prejudice undermines him with thoughts akin to "I am not attractive," "I am not worthy of Desdemona," "It cannot be true that she really loves me," and "If she loves me, then there must be something wrong with her."
These thoughts, inflamed by Iago's hints and lies, prevent Othello from discussing his concerns and fears directly with Desdemona, and so he acts on panicked assumption. In order to survive the combined onslaught of internalized prejudice and the directed venom of Iago, Othello would have had to be near perfect in strength and self-knowledge, and that is not fair demand for anyone.

Othello and Iago are are similar because of their fallibility. Iago is overcome with his desire for revenge to such an extent that he puts it into action. Othello's love and possessiveness of Desdemona take over him until he eventually would rather kill her than allow anyone else to have her. In this way, despite their contrasts, Iago and Othello both represent the extremity of the same thing - human emotion

When reading Shakespeare's "Othello the Moor of Venice", the two main hero's seem to be very different, both in character and actions.
Othello seems to be an honest man who believes other people. He is respected by society for his nobility and bravery. Iago is a villain, plotting around not only against Othello. Othello demotes him to a lower status, and despite beeing a trained soldier, Iago is quite a coward when it comes to confronting an enemy with a sword.
Although these two figures seem so different, they are [much more] alike, in more than one way. They both share the army way of life, and they tend to curse and use harsh language when upset. They both betray the people they are close to.
Othello and Iago are suspicious towards their wives, threaten them and eventually murder the innocent women.[In this essay we will see that] [D]despite their differences, Othello and Iago are two soul mates, that one way or another let their inner darkness out [and][TO] rule their actions.
One way in which these two characters differ is in their character.
From the beginning of the play, Othello lets Iago get close to him despite the fact that Iago is expected to be jealous of Cassio. This trust develops throughout the play. "O, thou art wise; 'tis certain" (IV, i, 72), Othello says to the villain, completely blinded by his lies. Iago, as can be seen from act one, made up his mind to ruin Othello. "I follow him to serve my turn upon him" (I, i, 42), he tells Roderigo, as he describes the plot against Othello. Another difference is in the way they are viewed by others.Othello is so respected for his services[,] that he doesn't fear any complaints from Barbantio. [HE PROUDLY STATES,]
"My services which I have done the signiory
Shall out-tongue his complaints" (I, ii, 19).