Just the Facts

Name: Goes by the title 'The Doctor'. His true name is unknown, as is the reason for why he wishes it to remain hidden. He occasionally adopts a alias name such as 'John Smith.'
Species: Time Lord.
Age: 903 years old.
Sex: Male.

Physical Characteristics

• The Doctor appears to look like a white, Caucasian male.
• He has a binary vascular system - two hearts,
• A respiratory bypass system - meaning he can go for a while without oxygen,
• And an internal body temperature of 15–16 degrees Celsius.
• He is quick to heal,
• Shows heightened levels of stamina,
  
• High levels of pain intolerance,
• And also has to ability to survive where others would not, such as being directly hit by a lightning bolt.
• All other physical characteristics change as the Time Lord regenerates - he remains the same, yet every single cell in his body changes. This grants him the ability to cheat death.
• It has been noted that all Time Lords have 13 lives.
  

Intelligence:

• The Doctor is incredibly intelligent, and he knows it.
• He has shown amazing mathematical ability.
• And knows almost the entire history of Earth.
• It has been mentioned that he knows the name of every single star that has ever existed,
• And details on every life form that has ever existed, though he can not always identify them straight away.
  
• Because of his brilliant mind, there has been occasions in which enemies have sought to either control him, or steal his memories and acquire his intelligence for themselves.
• The speed at which his mind works is more clearly seen in the tenth Doctor, as he often lapses into long and complicated sentences of 'techno-babble'

"Rose: That thing, is it trapped for good on video?
The Doctor: That's right. But just to be on the safe side though, I'll use my unrivaled knowledge of trans-temporal extrapolation methods to neutralize the residual electronic pattern.
Rose: You'll what?
The Doctor: I'm gonna tape over it."

Psychic Ability:

• He has a low level of psychic ability.
• Is able to enter others minds and read peoples thoughts.
• On several occasions, he has used his psychic ability in order to fight and overcome enemies.
• Despite this ability to deeply understand another's mind, The Doctor often never opens up himself to others and appears as not wanting to become to close to anyone.

Family:

• The first Doctor traveled with his granddaughter,
• The second Doctor mentions that his memories of his family are still alive (though he never says that they are dead.)
• The eight Doctor recalls experiencing a 'beautiful Gallifreyan night' with his father.
• By the time of the ninth Doctor, the Time War has occurred and it is assumed that all of The Doctor's family are now dead.
• The tenth Doctor is noted say that he used to have a brother - Which in some accounts is believed to be Braxiatel

Life:

• Little is known of The Doctor's childhood, other than it was a lonely one.
• When he was on Gallifrey, he was often known as Theata Sigma - which was a sort of nickname.
  
• When at the Academy, he was part of a group of young rebellious Time Lords, known as the Deca.
  
• He was not contented with living by the Time Lord code of remaining on Gallifrey, and never interfering with any other race - So he stole a TARDIS from a docking bay where it was being dismantled for scrap.
• Since then he has traveled through time and space most often with 'assistances' or 'companions.'
• He was elected as the 407th President of Gallifrey, although he did not want the job and instead opted to travel once again, leaving Gallifrey in his tutor Borusa's hands. Although he returned briefly to take up his presidency in order to defeat the Vardins and Sontarans, he departed soon after, again leaving Gallifrey to Borusa.