It depends on the specific story. Different stories have different antagonists. Sometimes it could be a villain with evil intentions, and other times it might be a character with opposing goals to the protagonist.
An antagonist is basically a character or a force that opposes the main character or protagonist. They create conflicts and obstacles for the hero to overcome.
The villain can be an antagonist in story. For example, in the 'Harry Potter' series, Voldemort is a clear antagonist. He tries to harm the main characters and has goals that are opposed to the heroes.
Antagonists are often self - centered. They focus on their own desires and don't care much about others. Take Captain Hook in 'Peter Pan'. All he cares about is getting revenge on Peter Pan and ruling Neverland for himself.
The villain can be an antagonist in a story. For example, in many superhero stories, the super - villain like the Joker in Batman comics is a classic antagonist. They oppose the hero and create conflict.