What is the characterization of Othello?
If you are speaking of the characterization, that is how other characters construct him, it depends on who is characterizing him. He is spoken of most often by Iago, who refers to him constantly as a "Moor", and uses animal imagery whenever he makes reference to him. So the insinuation from Iago's perspective is that he is beast-like.
He describes himself as "rude in speech" and untutored, but he is hardly that. He certainly speaks well enough to infatuate (not in a sexual sense) Desdemona's father, and to seduce Desdemona.
He is brave and adventurous, he is in fact the best general the Duke has at his disposal. He is confident in battle; however, he is not confident with people. He may not actually be "rude in speech" but the fact that he thinks of himself this way (if this was not a rhetorical move) suggests that in social situations he feels somewhat inferior to others. This is significant because he is quick to credit Iago with having a superior understanding of people. And it is true. In battle, Othello would never trust something to be as it appears, yet he states that he expects people to be on the inside as they appear to be on the outside. It is this naiivete that leaves him open to Iago's manipulation. He trusts that what Iago tells him is true. Yes, he asks for truth, but even as he asks he listens and is convinced. It may be that his insecurity plays a part here as well; although he resists Iago's initial suggestion that Desdemona might want someone more desirable than him (he at first counters Iago by saying that he is who he is and yet Desdemona still chose him) he is very quickly willing to believe that she would fall for someone like Cassio.
He is intensely passionate: he loves hard and he hates hard. Even before his jealousy of Desdemona mounts, he says he feels his passions override his intellect when, angry at the fact that his guards have been fighting, he tells them that he is so angry that he is afraid he will strike at the wrong man.
Although he is no animal, he is too often ruled by his emotions. A good ruler should have control over his passion and should allow the better part of man (his intellect) to guide him.
Othello, a Moor, is a general of the Venetian army. At the beginning of the play, he has great successes and all is going well for him. He's sent to Cyprus to defend it against the Turks. Then he marries Desdemona. At this point, he's still confident and self-controlled. This confidence begins to decline when Iago suggests Desdemona is having an affair with Cassio. He thinks his skin color, older age, and lack of courtly charm makes it inevitable that his wife would cheat on him. Iago works Othello into a jealous rage which leads to him killing Desdemona. He justifies killing her by saying he's saving her good name. From beginning to end, Othello changes from a heroic leader to a "savage beast" because he's so easily manipulated by Iago. Iago knows Othello is unsure of himself in civil society. In the end, Othello is an outsider, a hired gun of Venice, who commits murder.