The protagonist is the main character or hero that we cheer on and hope conquers all.
The antagonist is the story's villain. The best bad guys are the ones we love to hate. We don't need to know why they are bad, we don't need a play by play of the choices they made early in life, we simply recognize they are bad and we don't want them to win.
A story can operate without an antagonist; however the use of an antagonist is the best way to demonstrate conflict within a storyline.
Conflict in a well executed work of fiction provides the friction that keep readers tuned in. In most cases the antagonist reigns supreme through the majority of storyline. The reader wants the forces of good to triumph, yet the villain remains in charge of the bulk of events that thread through your tale.
This combination of good versus evil creates suspense and causes your reader to wonder how exactly the protagonist will gain an advantage.
One of the primary benefits fictional conflict is the reader is often forced to consider how they might respond against such odds and in similar circumstances. In a best case scenario the story assists the reader in learning more about themselves.
Conflict can also be used to disrupt a normally predictable plot. By presenting conflict that is, in many ways, worse than the previous conflict you can instill a greater desire for evil to be defeated while keeping the reader guessing where the story may be headed next.
Ultimately the story must provide resolution. For the fiction writer of faith this resolution process often provides the simple message that good will triumph over evil although other threads of faith will likely work their way through your text ? sometimes without you being consciously aware of their presence.
If you allow the antagonist to loose the struggle too early in your story it becomes anti-climactic and the fire in the story is reduced to an ember that may leave your audience cold.
The use of a villain (may not be a human, could be an animal, ideal, political agenda, etc.) goes a long way in conveying a story with elements that emotionally involve your reader.
