What is the characterization of Feste based on his role and function especially in relation to the other characters?
The role of Feste in Twelfth Night is that of Fool or Court Jester to Countess Olivia. One of Feste's functions is to give the audience insight to the characters whom he knows better than anyone because the convention was to be genuine in front of Jesters. Shakespeare employs two categories of characters to perform this function of insightful revelation. He employs Clowns and Fools. Many people think of these two categories of characters as being identical with interchangeable terminology, whereas to Shakespeare there were specific distinctions between the Clown and Fool.
The Shakespearean Clown is a country person and usually operates in a pastoral setting. The Clown gives information about the other characters by accident, not by insightful observation. The Clown engages in wordplays because he doesn't know what he is saying, not because he is exercising great wit. The Fool on the other hand is an urban character who operates in palaces and such settings. The Fool gives information about characters because of insightful observations. The Fool engages in wordplay intentionally because of his great wit and often with a profound meaning in mind. Feste, by these definitions, is a Fool operating in a humorous and insightful role by intelligence and intention.
One of Feste's primary functions is to let the other characters have an objective view of themselves and their behavior. Olivia, Orsino, and Viola take no offense at Feste's remarks and observations because they are indeed insightful, as he says of himself, "I wear not motley in my brain." However, Malvolio does take offense at Feste's words as well as having contempt for Feste's wittiness with words.