This is a television series produced by the BBC
between 1963 and 1989 about a time-traveller. The series in its early years alternated historical dramas with science fictional stories (it was supposed to be educational). However by the late 60's it was only science fiction (The last purely historical story was "The Highlanders").
The first episode of Doctor Who ("An Unearthly Child") was transmitted on 23 November 1963 - the day after the assasination of President John F. Kennedy. This meant that many people missed it and it was repeated before the second episode was transmitted.
The series was originally in black and white and only became colour with the introduction of the third Doctor (played by Jon Pertwee) in the 1970 story "Spearhead from Space".
The series became popular in the US with the adventures of the fourth Doctor (played by Tom Baker). He played the Doctor for the longest (7 years and 41 stories - not counting the uncompleted story Shada).
Though there have been only 8 Doctor characters on TV (including Paul McGann in the recent TV movie) 9 actors have played the Doctor on TV. When the story "The Five Doctors" was made William Hartnell had died so the first Doctor was played by Richard Hurndall.
Two Doctor Who movies were made in the 60's starring Peter Cushing based upon two Dalek stories from the time of the first Doctor.
Amongst many memorable creatures from the series were Daleks, Cybermen, Sontarans, and Yetis.
The Doctor and his companions travelled in the TARDIS which was shaped like an old style blue British Police Box.
The doctor often travelled with one or more companions. He also sometimes worked with the Earth organisation U.N.I.T. as a scientific advisor.
The central character was referred to simply as "The Doctor". The BBC were very strict about not referring to him as Doctor Who (and also objected to the abbreviation Dr Who for the series).