What's a Protagonist?
In simple terms the protagonist is also commonly known as the main character, they are vital to any plot in any story regardless of genre.
The protagonist or main character is central to the plot. Usually the protagonist is deeply affected by a situation which they must successfully resolve usually involving conflict.
The source of their conflict or antagonism is the antagonist, another character that is key to plot development.
There is always a protagonist in every story but interestingly they do not have to be a single character. They can be a group of people, an animal robot, race of people.
It is very important for the protagonist to go through change when faced with their conflict, and it needs to be satisfying to the reader. This could be personal growth and improvement which they go through in order to solve their conflict.