The Doctor's Tardis

The Tardis stands for Time And Relative Dimension(s) In Space. The Tardis is the Doctor's Ship in the form of a 60's Police Box. The Tardis is bigger on the inside that on the outside. The inside of the Tardis has been changed and for the fifth season, a brand new inside for the Tardis was constructed which is now bigger than ever and up-to-date with modern time (funky).

In theory its "chameleon circuit" should allow it to appear as any common object to avoid arousing suspicion. But a technical fault jammed the system in 1963 leaving it resembling a police box ever since.

Dimensionally transcendental
The signature feature of a TARDIS was that the interior exists in a different dimension than the exterior. The main application of this concept was that it was a different size on the inside than the out. With the exception of Iris Wildthyme and Professor Chronotis' TARDISes, this meant that they were bigger on the inside than the outside. (DW: The Robots of Death).It has also been suggested in that the Doctor can use this technology on objects other than the TARDIS, as he pulls a large remote control from his pocket, and when asked how it fit in there, he responds, "They're bigger on the inside!" (DW: The Runaway Bride). Again this can be seen frequently with the Fourth Doctor whenever he is asked to empty his pockets, as he proceeds to bring out many items that would not have fitted inside a normal pocket. An example of this is when the Doctor is captured and interrogated (DW: Genesis of the Daleks), and when loading the make shift grenade launcher he says "Empty your pockets..... Leela you better help me". (DW: Horror of Fang Rock)

Chameleon circuit
An obvious feature of all TARDISes was their ability to blend into their surroundings once they landed. If working properly, a chameleon circuit would assess the surroundings just before arrival and change the exterior to resemble a thing common to that landscape. (DW: An Unearthly Child, Rose, Boom Town) On the one occasion he got it working, the Doctor's chameleon circuit appeared to give him no control over the change, as it was an automatic circuit. (DW: Attack of the Cybermen) Later models may have allowed greater flexibility. The Master's ability to produce an ionic column in incongruous environments (DW: Logopolis, Castrovalva, Time-Flight), as well as the Monk's statement that he chose to make his TARDIS look like a sarcophagus (DW: The Time Meddler), perhaps indicated that the circuits of later models could indeed be manually operated. This theory is further substantiated when the doctor enters the Monk's TARDIS and changes it's appearance from a pillar of stone to a police box identical to his own TARDIS (DW: The Daleks' Master Plan) . In Logopolis, it is implied that the Doctor could select what the TARDIS would look like. He even demonstrates to Adric how he would change the TARDIS into a pyramid, if the chameleon circuit were functioning properly.

Organic machines?

TARDISes were incredibly complex machines. The nature of their construction was such that they were said to be grown rather than constructed (DW: The Impossible Planet), thus simulating a biological process though it is not clear whether this is indicative of the machine being biological in nature or simply so intricate and complex as to appear to mimic the processes of a biological entity. The TARDIS is grown from TARDIS coral; during his tenure with Torchwood 3, Jack Harkness had a TARDIS coral growing in his office (though it would take hundreds of years to attain maturity).

Due to the level of complexity in their construction, TARDISes had a certain degree of sapience, and could take independent action, such as when the Doctor's TARDIS resurrected Grace and Chang Lee (DW: Doctor Who (1996)), or non-Time Lords looking into the heart of the TARDIS had varying results. (DW: Boom Town, The Parting of the Ways)

Due to conflicting evidence from various sources, such as other Time Lords and the Doctor himself, it is unclear to what extent the average TARDIS is alive, and whether that life extends beyond artificial sapience and into a biological existence. Some more-advanced TARDISes, such as Compassion, have been fully-sapient beings in their own right.

TARDISes often "mourned" the death of their Time Lord pilots, even going so far as to commit suicide by flying into a sun or simply hurling themselves into the Time Vortex. The Fifth Doctor claimed there was "an elephants' graveyard" of TARDISes somewhere at the end of time. (BFA: Omega, The Axis of Insanity)

Because the TARDIS displayed these organic traits, the Doctor considered his TARDIS to be alive. He talked to and stroked parts of the TARDIS when he operated it. (DW: School Reunion) He diagnosed mechanical difficulties as medical conditions like "indigestion." (DW: The Runaway Bride) He once commented that a TARDIS was "more like a person." (DW: The Five Doctors) Even the Supreme Dalek invited the Doctor to "feel it die", when he believed he had successfully destroyed the TARDIS. (DW: Journey's End) In at least some situations, Time Lords could give up some of their life essence to power up a TARDIS. (DW: Rise of the Cybermen) In at least one case, the Doctor's TARDIS manifested an avatar to help him fight a mental battle, taking on the forms and personas of the various companions who had ridden within it (IDW: The Forgotten).

Video Of New Tardis

Source: BBC