What is Gallifrey, and why is it important to the Doctor's backstory?

Gallifrey is the home planet of the Time Lords in the television show Doctor Who. It is the planet on which the Doctor was born and raised, and is central to the show's mythology and the character's backstory.

Gallifrey was first introduced in the 1969 serial 'The War Games' as the home planet of the Time Lords, an ancient and powerful race of time-travelers. The Doctor, played by various actors over the years, is a Time Lord himself, and fled his home planet in a stolen time machine, known as the TARDIS.

The Time Lords are known for their advanced technology, including their ability to regenerate when they are near death, allowing them to take on new appearances and personalities. The Doctor has gone through many regenerations over the course of the show's run, each played by a different actor.

Gallifrey has been the setting for many episodes of Doctor Who, and is a key part of the show's mythology. The Doctor's complicated relationship with his home planet, as well as the Time Lords themselves, has been explored in depth over the years.