This is a summary of 'Othello' written by William Shakespeare in my own words.
(Exposition) The play opens one early morning with a Venetian man, Iago plotting revenge on a moor, Othello with his accomplice, Roderigo. Othello promoted a man called Cassio which infuriated Iago because he was passed in military rank. They are in a street and knocking on Senator Brabantio's door to alert him that his daughter, Desdemona, secretly wants to marry Othello. People in Venice aren't fond of Othello because he's 'a man of colour' and Barbantio later accuses him of seducing his daughter with witchcraft before the Duke of Venice but she denies it.
(Conflict) Othello is sent to Cyprus to fight the war against Turks on a ship with Desdemona, Iago and his wife Emillia. (Rising action) Iago decides to take advantage of Cassio, the man who stole his promotion and uses his henchman Roderigo to set up a fight between them which ultimately results in Cassio's demotion. Iago then, acting concerned for Cassio advises him to ask Desdemona to speak with Othello about considering to promote him back. As Othello and Iago enter the next scene, Cassio hurriedly leaves and Iago points out how he seems to be avoiding Othello. Desdemona then appears and earnestly begs for Cassio's reinstatement. Iago "connects the dots" for Othello and plants a seed of doubt in his mind, implying that Desdemona is in love with him.
(Climax) Desdemona loses a handkerchief which Iago claims to Othello that she gave it to Cassio. He also stages a conversation with Cassio which makes Othello all the more suspicious of the faithfulness of his wife. Finally unable to bear it, Othello decides that Iago and him will murder the two.
Iago and Roderigo go out to kill Cassio late at night. Roderigo is killed but Cassio is left injured. Hearing cries of his pain, Othello advances to fulfill his part. (Falling action) As Desdemona comes once more to ask for Cassio's reinstatement, Othello accuses her of being unfaithful and smothers her in bed with a pillow.
Emillia confronts Othello and alerts people before being stabbed by Iago. When Iago's malicious plot is uncovered, Othello sees that he has been fooled and stabs himself, dying next to Desdemona. (Resolution)
Reference: http://www.cliffsnotes.com/literature/o/othello/play-summary