In Doctor Who, the police-box-shaped time machine is called the TARDIS. The name is an acronym for “Time And Relative Dimension In Space,” describing its ability to travel through both time and space.
The Doctor’s TARDIS is a machine and spacecraft belonging to the Time Lords of Gallifrey. Its exterior normally resembles a blue British police box, but its interior is famously “bigger on the inside.” This impossible spatial difference is explained in the series as a dimensionally transcendental design.
The police-box appearance is not the TARDIS’s intended form. Its chameleon circuit is supposed to disguise the machine according to its surroundings, but the Doctor’s circuit becomes stuck, leaving it permanently disguised as a 1960s-style police box. The design was familiar British street furniture when Doctor Who began in 1963.
A common mix-up is calling it a phone booth. A police box was a communications and shelter point used by police officers, whereas a phone booth was intended primarily for public telephone calls. The DeLorean is the time machine from Back to the Future, not Doctor Who.