The protagonist of a story is the main character in a given work of literature, drama, cinema, or other narrative work. It is a common misconception that the protagonist is always the "good guy" of a given story — this is not necessarily the case, as protagonists can just as easily be evil characters. They are the characters around whom the events of a narrative circulate and with whom the reader is meant to empathize. In many cases, such characters are placed in direct opposition to another character, force, or institution, referred to as the antagonist. Protagonists tend to undergo some important change emotionally or philosophically during the course of their struggles against antagonists.
A protagonist is, in many cases, referred to as the "hero" or the "main character" of a story. Though there are no set rules defining what makes an effective protagonist, such characters tend to be complex and detailed. Directly or indirectly, readers become aware of the main character's emotions and are generally able to empathize with the personal challenges that he faces over the course of the narrative. While many stories are primarily focused on events, others use events as tools to shape and change the protagonist's mental and emotional state. These changes, and not the events themselves, are often the focus of the narrative.
In spite of the common use of the word "hero," there is no need for a protagonist to actually possess heroic or even good traits. Some protagonists are cowardly and weak while others are unambiguously evil. Narratives with protagonists of this sort can be interesting because they explore the emotions and motivations of characters with whom a reader might not expect to relate. In narratives with heroic main characters, it is often easy for the reader to perceive the antagonist as a flatly evil character with selfish and horrible intentions. A well-written antihero, however, can evoke empathy from the reader, thereby humanizing a character that might otherwise be seen as flatly evil.
Some narratives actually have several different protagonists. This is particularly common in stories with multiple subplots, such as most novels in the epic fantasy genre. The main plot concerning the primary conflict of the entire work may have a primary protagonist. Other characters, who may simply be supporting characters in the main plot line, are often protagonists of their own subplots. Using a supporting character as a protagonist in a subplot allows a writer to develop secondary characters whose emotions, motivations, and other complexities are important parts of the overall narrative.