You are probably already adept at identifying the characters of a story, but there are some terms that will be helpful in your literary analysis. Keep in mind that characters aren't necessarily people. They can be animals, divine beings, personifications, etc.
One of the most important terms you will use is conflict. Conflict occurs between two opposing sides in a story, usually centering on characters' values, needs, or interests. A conflict can be internal or external. Internal conflict takes place within an individual, such as when a character is torn between duty to his family and duty to the state. External conflict occurs when two individuals or groups of individuals clash. A struggle between a character and his best friend is an example of an external conflict.
By examining the conflict, we can determine the protagonist and antagonist. The protagonist is the focal point of the conflict, meaning that he or she is the main character of the story. All the action in a story will revolve around its protagonist. In addition, a story that contains a series of conflicts can contain several protagonists--no story is limited to just one. The antagonist is the character who stands in opposition of the protagonist. The antagonist is the other half of the conflict. Remember that an antagonist doesn't have to be a person--it can be a nation, a group, or even a set of ideas.
Sometimes, the protagonist can take the form of the antihero. The antihero is a protagonist who does not embody traditional “heroic” values. However, the reader will still sympathize with an antihero. For instance, a protagonist who is a scoundrel is an antihero, as a traditional hero would embody virtue.
In addition to the protagonist and antagonist, most stories have secondary or minor characters. These are the other characters in the story. They sometimes support the protagonist or antagonist in their struggles, and they sometimes never come into contact with the main characters.
Authors use minor characters for a variety of reasons. For instance, they can illustrate a different side of the main conflict, or they can highlight the traits of the main characters. One important type of minor character is called a foil. This character emphasizes the traits of a main character (usually the protagonist) through contrast. Thus, a foil will often be the polar opposite of the main character he or she highlights. Sometimes, the foil can take the form of a sidekick or friend. Other times, he or she might be someone who contends against the protagonist. For example, an author might use a decisive and determined foil to draw attention to a protagonist's lack of resolve and motivation.
Finally, any character in a story can be an archetype. We can define archetype as an original model for a type of character, but that doesn't fully explain the term. One way to think of an archetype is to think of how a bronze statue is made. First, the sculptor creates his design out of wax or clay. Next, he creates a fireproof mold around the original. After this is done, the sculptor can make as many of the same sculpture as he pleases. The original model is the equivalent to the archetype. Some popular archetypes are the trickster figure, such as Coyote in Native American myth or Brer Rabbit in African American folklore, and the femme fatale, like Pandora in Greek myth. Keep in mind that archetype simply means original pattern and does not always apply to characters. It can come in the form of an object, a narrative, etc. For instance, the apple in the Garden of Eden provides the object-based forbidden fruit archetype, and Odysseus's voyage gives us the narrative-based journey home archetype.