Story structure
Protagonist
The main character of a story, whose key decisions drive the plot and whose fate the reader follows most closely.
A protagonist, from the Ancient Greek prōtagōnistḗs, "one who plays the first part, chief actor," is the main character of a story. The article's marks of the role: the protagonist "makes key decisions that affect the plot," is often the character "who faces the most significant obstacles and choices," is the one "whose fate is most closely followed by the reader or audience," and is opposed by the antagonist. Hero and protagonist are not the same thing: villain protagonists run from Humbert Humbert to Walter White, a false protagonist like Marion in Psycho can anchor the story before it moves on, and each subplot may have its own protagonist.
In craft terms the role is the holder of the want versus need pair and the vessel of the character arc: whoever makes the key decisions pays the story's price.