Final answer:
The antagonist is an opposing force to the protagonist, and it is not always bad or even a person; it can be an abstract concept. The role of the antagonist is to challenge the protagonist, contributing to the conflict and narrative progression.
Step-by-step explanation:
An antagonist is the opposing force to the protagonist within a story. While often thought of as the villain, an antagonist can take various forms such as an individual, a group, a force of nature, a societal norm, or even an internal struggle.
The primary role of the antagonist is to present challenges and conflicts that the protagonist must overcome.
This character or force significantly affects the narrative's progression and the protagonist's development. For example, in William Shakespeare's 'Hamlet', the antagonist is Claudius, while in Sophocles' 'Antigone', it is Creon.
Nonetheless, an antagonist is not always an evil character but one that stands against the protagonist's goals.
The protagonist, in contrast, is the main character and often the hero of the story. However, the protagonist can also be an antihero - a central character who does not have traditional heroic qualities.
An antihero may exhibit morally ambiguous behavior but still garners audience sympathy.
A notable example is the character of Satan in John Milton's 'Paradise Lost', who is considered the protagonist despite his traditionally villainous role.