The Doctor is a man from the planet, Gallifrey. He has had 10 previous incarnations and is currently in his eleventh, which is played by newcomer, Matt Smith. His race are (or were) the Time Lords, but they were wiped out by the Daleks and the Last Great Time War, with the Doctor being the only survivor, that was until villain, The Master, found a link to bring them to our time, but they were soon sent back. He travels in the TARDIS which stands for
Time
And
Relative
Dimension
In
Space. He has had companions such as Rose Tyler, Donna Noble, Martha Jones, Astrid Peth, Captain Jack, Lady Christina, Adelaide and Wilfred Mott. Just recently he regenerated after absorbing radiation to save Wilf. He is younger and is "still not ginger"! The Eleventh Doctor's adventures will begin this Spring.
Just a bit of information:
I don't know if you can take the show to a literal point but I believe the Doctor said that he was the cause of the end of the Timelords.
He won the war by destroying both sides, or so he thought, Daleks, the Master, etc.