Doctor Who is a British science fiction television series that first aired in 1963. It 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 British police box on the outside. The Doctor is often accompanied by companions and faces various alien threats while exploring different historical periods and futuristic worlds. The show is known for its imaginative storytelling, iconic characters, and the ability of the Doctor to regenerate, allowing different actors to portray the character over the years. This unique aspect has contributed to its longevity and popularity, making Doctor Who a beloved part of British pop culture.