Who are the protagonist and antagonist?
A really valuable book on writing is The Art of Dramatic Writing by Lajos Egri. (See reference link below.) He defines a protagonist as the character whose motivation makes everything happen. The antagonist is the character who opposes the protagonist. The antagonist does not necessarily have to be human. And the protagonist does not necessarily have to be human. But one or the other should be human. A protagonist is obviously more important in a play or movie because they involve people interacting with people. If a man is trying to conquer Mount Everest in a story, the man is the protagonist and the mountain is the antagonist, which would make it a "Man against Nature" story. If a man is trying to survive in a flood, as in William Faulkner's "The Old Man," that would make it a "Nature against man" story, and nature would be the protagonist. Godzilla is the protagonist in that awful movie. The protagonist, according to Lajos Egri, should be so strongly motivated that he, she, or it will drive the story to the very end. Dorothy is the protagonist in The Wizard of Oz. She is just a little girl, but she is determined to get back to Kansas. In Ernest Hemingway's short story "The Killers," the protagonist does not even appear. He is the unidentified "friend" in Chicago who wants Ole Andresen killed. Ole, of course, is the antagonist. In Hemingway's short story "Hills Like White Elephants," the protagonist is the American and the antagonist is the girl he calls Jig. He wants her to have an abortion, and she wants to have the baby.
If this is meant to be a general exploration of the topic, definition of terms would be essential here. The protagonist is the central character or figure in a work. It is usually through their eyes or their perception that the author wants us to understand the central conflict of the work. The protagonist is sometimes likable, and sometimes demonstrates behaviors that are not entirely likable, but they are our "guides" for lack of a better term. For example, in the drama Oedipus by Sophocles, the protagonist is the lead character for whom the title of the play is derived. The antagonist is someone who, in their name, "antagonizes" the protagonist. They are the individual against whom the protagonist is set against. The antagonist "opposes the hero or protagonist in drama." For example, Abigail Williams in the antagonist in Arthur Miller's work, The Crucible. She operates as the antagonizing force to John Proctor, who is the drama's protagonist. In distilling both characterizations, I would look for the central conflict in the work in question and which characters stand on which side of said conflict.
I don't know if you are asking for someone to identify the protagonist and antagonist in a particular piece of literature, or if you are just asking for the definition of the terms. If you would like someone to help you find who they are in some work you are reading, you need to identify that work for us so we can help you.
If, however, you are just looking for definitions, a protagonist is not simply the good guy, and the antagonist isn't just the bad guy. They often take on those roles in literature...but since a good character has shades of good and bad, we can't just give them white or black hats.
A protagonist is the character whose struggle we are following during throughout the plot of the story. The antagonist is the person/thing that gets in the way, or tries to block the protagonist from reaching his or her goal.
The protagonist in a piece of literature is the main character. Oftentimes, this will be the "good guy" with the noble purpose, but this really doesn't have to be the case. The antagonist, on the other hand, is the individual in opposition of the protagonist. Again, this is commonly considered the "bad guy" but that is not always necessarily true. The central conflict of the story will be between the protagonist and the antagonist, so that is one method to identify which out of the many characters are the protagonist/antagonist, though it will not tell you really which is which.
Conflict is generally thought to be at the heart of engaging literature and drama. For conflict, you need a clash. Thus, the protagonist goes head to head against the antagonist. This importance of conflict in tragic literature was first recorded by Ancient Greek scholar, Aristotle.
This clash need not necessarily be between two people. There can be a number of antagonists who the protaganist must deal with. Society can be an antagonist. Even, the protagonist's own weaknesses or doubts can be a form of antagonist. Where there is conflict in literature and drama, there is a protagonist and antagonism. Sometimes, people, society and the self can all be antagonisms, such as in The Catcher in the Rye, by JD Salinger.
Thus, it can be said that the protagonist is the main character of the book, and the antagonists are all the impediments who s/he faces. Most works tend to have one main antagonist or "nemesis" which gives the narrative a sense of personal contest. In The Catcher in the Rye, however, although Holden conflicts against a number of people, it is ultimately society as a whole, as seen through the prism of his own mental problems, that are his antagonist.
protagonist is the good guy. and the antagonist is the bad guy, who is against the protagonist.
PROTAGONIST IS MAIN HERO OF THE PLAY AND ANTAGONIST IS A CHARACTER WHO SUPPORT NOT ONLY TO HERO BUT TO DEVELOP PLOT.