"simp7fan;c-1846497" wrote:
So, how does Dr. Who work? They're different people...and now different genders. What does it all mean?
The Doctor is a Time Lord (which is a subset of being Galifreyan). When badly damaged or extremely old Time Lords can Regenerate. If it's voluntary (i.e. "This one's getting too old, I think it's time to regenerate") they can control the regeneration. The Doctor's regenerations tend to be random because of extreme injuries (falling from great heights, being shot, poisoned, etc).
How this came about:
The Doctor was originally played by William Hartnell, who was quite old and in poor health at the time. The show was massively popular so they didn't want to end it so they had to come up with some way to replace him (plus he had become the epitome of "Crotchety Old Man", having become impossible to work with, forgetting his lines, missing his marks, being out sick, etc). One of the ideas they came up with was "Renewal" (later changed to Regeneration) which is what they went with.