Marty McFly
Marty McFly is a high school student and the protagonist of the Back to the Future series. He is accidentally sent from 1985 to 1955 in a time-traveling DeLorean invented by Doc Brown. His actions in the past alter his family's future, making him the central driver of the story.
Doc Brown
Doc Brown is a fictional mad scientist and inventor who creates the flux capacitor that enables time travel. He provides Marty with guidance and technical support, and his experiments directly trigger the events that connect the different timelines in the franchise.
Biff Tannen
Biff Tannen is the primary antagonist across the Back to the Future timeline. He is a bully who intimidates Marty and his family, and in the alternate 1985 timeline he gains control of a corrupt business empire through interference with the past.
For more details on the main characters and their roles, see the overview at https://en.wikipedia.org/wiki/Back_to_the_Future.
