A literary text tends to include two types of main characters--the protagonist and the antagonist. A protagonist is the main character of the text (typically the narrator, if a first person narration, or the main character the text follows). The antagonist is the character, or entity, the protagonist conflicts with. In some cases, the antagonist can be another character, a supernatural being (like a ghost, spirit, or the Devil), or an element in nature (an animal, storms, cliffs, or ice fields).
The main protagonist in Chris Lynch's Gold Dust is Richard Riley Moncrief, the story's narrator. Richard loves baseball, and he wishes to share his love of the game with Napoleon Charlie Ellis, a boy from the Dominican who is in seventh grade (again).