An antihero is the main character of a story, but one who doesn't act like a typical hero. Antiheroes are often a little villainous.
Traditionally, the protagonist — main character and focus — of a story has been a hero: someone good, noble, and brave. However, some stories change things up by having an antihero instead. An antihero may not be heroic at all. TV shows have featured antiheroes who are mobsters, drug dealers, crooked cops, and even serial killers. An antihero is kind of like a villain, or a mix of a hero and a villain. Antiheroes are complex characters, which is why they’re popular.