|“||It's bigger on the inside!||”|
- "A TARD, haha. Like something's stupid!"
~An insightful American's opinion on the etymology of the TARDIS' acronym.
The TARDIS is one of the Doctor's wives along with The Abzorbaloff and River Song. It's also a time machine/spaceship that uses the Time Vortex to travel the universe while The Doctor abducts companions.
The TARDIS is up and downy stuff in a big blue box. It is a product of the advanced technology of the Time Lords. A properly piloted TARDIS can transport its occupants to any point in time and any place in the universe.
The interior of a TARDIS is much larger than its exterior, which can blend in with its surroundings using the ship's chameleon circuit. The Doctor's TARDIS is stuck looking like a police telephone box from the 1960's. The Fourth Doctor tried to repair it in Logopolis and the Sixth Doctor fixed it in Attack of the Cybermen and it materialises as a pipe organ and a tomb among other things. Sixie later ate the circuit and the TARDIS became a police box again.
The unpredictability of the TARDIS's guidance system has often been a plot point in the Doctor's travels. In The Doctor's Wife the TARDIS reveals that much of this "unpredictability" was actually intentional on its part in order to get the Doctor "where he needed to go" as opposed to where he "wanted to go". D'awwwwwwww.
It was also revealed in The Doctor's Wife that inside the TARDIS is a bitey mad lady called Sexy who the Doctor has been secretly banging for years.
The Doctor's TARDIS has had many different interiors (or desktop themes) over the years. On occasion we've also seen the Master and the Rani's TARDIS, which come with their own extra evil-looking interiors. Fans will spend hours arguing over which TARDIS set is best but they all have their various charms. Except your favourite one, which is shit. Unless it is also my favourite one.
You've redecorated haven't you? Looks like fucking shit. Edit
TARDIS stands for Time And Relative Dicks In Sluts, named that way after The Doctor's granddaughter saw him fuck eight sluts at the same time using his Relative Timedick. Strangely, all of these women also had dicks.