Stock characters are characters that fit into a stereotypical role or type, such as the villain, the hero, or the sidekick. They are often one-dimensional and lack complexity.
Flat characters are characters who have a single, dominant trait or motive, and do not change or develop throughout the course of the story.
Round characters are complex and well-developed characters who have multiple traits and motives, and who change or develop throughout the course of the story.
Characters can also be classified by their role in the story. Protagonists are the main characters of the story, and are usually the ones who drive the plot forward. Antagonists are the characters who oppose the protagonist and try to prevent them from achieving their goal.
Character development is the process of creating a character that is believable, relatable, and interesting. This involves giving the character a clear backstory, motivations, and goals, as well as developing their personality and relationships with other characters.
Characters are essential to a work of fiction, as they provide the reader with someone to relate to and follow throughout the story. They can also be used to convey themes and messages, and to explore different aspects of human nature.