"The Doctor" was the primary alias of a renegade Time Lord from Gallifrey who journeyed through time and space with various companions in his obsolete and "borrowed" Type 40 TARDIS.

Though largely a believer in non-violent conflict resolution, he was, when absolutely necessary, a great warrior. Indeed, some civilisations in the universe translated the word doctor as warrior, whilst others saw him as a compassionate benefactor, worthy of their admiration and compassion.

Numerous good deeds aside, he was indisputably responsible for billions of deaths at his conclusion to the Last Great Time War. He was virtually the only Time Lord survivor of that great conflict with the Daleks, largely because he ended it by obliterating both races. However, the Daleks kept returning despite his actions.

From the latter years of his first incarnation onward, he had a pronounced affinity for Earth and the human race. After departing Gallifrey, he voluntarily chose to spend time on the planet, choosing it as the place of his exile during most of his third incarnation, and even owning property in Kent, and New York City. He favoured Great Britain as a frequently visited location, taking most of his companions from there. Even before the destruction of Gallifrey, the Doctor spent much more time on Earth than on his homeworld.

The Doctor's true name remains unknown to all but a very few individuals, such as Samantha Jones, River Song and briefly Clara Oswald. His real name was not used by the Time Lords, even in the formal setting of legal trials. According to the Master, he chose this name according to a Gallifreyan custom to reflect his constant need to make people better.