Tragedy is one of the two great divisions of drama. In the Greek tradition which has come to us from Aristotle a tragedy is a play in which the audience witnesses the fall of a great man. The great man, or tragic hero, is better than the average person but he has enough of normal qualities so an audience can identify with him.
The tragic hero has a tragic flaw (hamartia) which leads to his downfall. Hamartia may be in the form of ambition or greed or any other vice. To the Greeks, the worst tragic flaw was hubris- pride or disregard for moral law. Those who stand in the way of the hero carrying out his wishes are know as his nemesis.

The Greek gods would not stand for moral laws to be broken and the hero who committed wrong always received his fate or just reward.
The world cries out for order to be restored and the protagonist (the good guy) always wins over the antagonist (the bad guy).
In the end, the tragic hero does not die a coward’s death. He remains a hero to the end.

The audience watching such a tragedy leaves the theatre with a feeling of catharsis or cleansing having seen the tragic hero destroyed and order restored to the world.
Macbeth, at the first of the play, is praised as a great man. He falls victim to his vaulting ambition and commits moral sin, murder.

The Elizabethans saw the world in two planes. There was the universe or large world which they called the macrocosm and the small world which they called the microcosm. If something went wrong in the small world (in the play or one’s life or even the kingdom) it would make the macrocosm out of balance. The evil deed would need to be revenged before the world would be right again.