A protagonist is the main character in a work of fiction, while the antagonist is the person who stands in opposition to the protagonist. The protagonist is sometimes referred to as the hero of the story, while the antagonist is often referred to as the villain.
In many stories, the line between hero and villain is not clear-cut. In some cases, a story has no clear-cut antagonist. Sometimes, it is a situation or an inner conflict that stands in opposition to a protagonist, rather than another single character. The main character of a story may not be heroic or admirable, and yet that person is still regarded as the protagonist. The word "protagonist" comes from the Ancient Greek word "protagonistes," meaning "one who plays the first part."