Doctor Who is a British science fiction television series that first aired in 1963. The show follows the adventures of the Doctor, a Time Lord from the planet Gallifrey who travels through time and space in the TARDIS, a time machine that looks like a blue British police box on the outside. The Doctor often travels with companions, facing various alien species and historical figures. The series is known for its imaginative storytelling, unique characters, and ability to regenerate the Doctor, allowing different actors to portray the character over the years. This regeneration concept has contributed to the show's longevity and popularity, making it a beloved part of British pop culture.