What are the characteristics of comedy and tragedy in plays?

A tragedy is distinguished by its unpleasant ending which frequently encompasses the death of the main character (Death of a Salesman, Hamlet) or his total destruction (Oedipus Rex).

A comedy generally has a happy ending for all concerned, and a plot which can contain elements of slapstick or farce. (But not necessarily--romantic comedies do not usually have such elements)

Many plays cannot be slotted into either category because the ending is ambiguous--happy for some and unhappy for others, or slightly more unhappy or slightly more happy than it was at the beginning for most or all of the characters. This is true of most modern plays but also some classical ones, such as Shakespeare's Troilus and Cressida.