A protagonist () is the main character in any story, such as a literary work or drama. 

The protagonist is at the center of the story, makes the key decisions, and experiences the consequences of those decisions. The protagonist affects the main characters' circumstances as well, as they are often the primary actor propelling the story forward. If a story contains a subplot, or is a narrative made up of several stories, then the character who is interpreted as the protagonist of each subplot or individual story. 

The word "protagonist" is used notably in stories and forms of literature and culture that contain stories, which would include dramas, novels, operas and films. In those forms the protagonist may simply be the leading actor, or the principal character in the story. More formally, the protagonist, while still defined as a leading character, may also be defined as the character whose fate is most closely followed by the reader or audience, and who is opposed by the antagonist. The antagonist will provide obstacles and complications and create conflict that test the protagonist, thus revealing the strengths and weaknesses of their character. 

The earliest known examples of protagonist are dated back to Ancient Greece. At first dramatic performances involved merely dancing and recitation by the chorus. But then in "Poetics", Aristotle describes how a poet named Thespis introduced the idea of having one actor step out and engage in a dialogue with the chorus. This invention of tragedy occurred about 536 B.C. Then the poet Aeschylus, in his plays, introduced a second actor, inventing the idea of dialogue between two characters. Sophocles then wrote plays that required a third actor.
what is a protagonist
who does it affect
how far back do protagonists go
who came up with the idea of having a main character out of the chorus
who reveals strength and weaknesses of protagonist
what does he provide
what year did this occur in Greece
who introduced the second actor
who introduced the third
what kind of "stories" include a protagonist
main character
A protagonist () is the main character
main characters
The protagonist affects the main characters' circumstances 
Ancient Greece
The earliest known examples of protagonist are dated back to Ancient Greece
Aristotle
But then in "Poetics", Aristotle describes how a poet named Thespis introduced the idea of having one actor step out and engage in a dialogue with the chorus.
The antagonist
The antagonist will provide obstacles and complications and create conflict that test the protagonist, thus revealing the strengths and weaknesses of their character. 
obstacles
 The antagonist will provide obstacles
unknown
unknown
Aeschylus
Then the poet Aeschylus, in his plays, introduced a second actor,
Sophocles
Sophocles then wrote plays that required a third actor.
dramas
The word "protagonist" is used notably in stories and forms of literature and culture that contain stories, which would include dramas, novels, operas and films. 