Everyone remembers Tom Baker's Doctor Who from the 70s - tall guy with a funny grin, curly hair and the long scarf. Overly long stories with lots of running around. Rubber suit monsters and cheap special effects.
Every so often the Doctor is wounded/injured and reboots (regenerates) into a new actor. Tom Baker was the 4th Doctor. Budgets got tight and the show finally ended in the 80s with the 7th Doctor. There was a made for TV movie in the 90s but it didn't catch on
This new series has been a lot different. Good scripts (mostly), nicely shot and good cgi/special effects work. Modern TV well done, basically.
Its one of the top 7 shows on the BBC right now ... huge audience.
The 1st new season has the 9th Doctor Who, played by Christopher Eccleston. I really got to like him (look up some of his other stuff - like "Shallow Grave" with Ewan McGregor, or "Second Coming"). He even did a small part on the NBC show "Heroes" last season.
The End of the World was the 2nd show of the first new season - the BBC just finished airing the 3rd season of the new series. SciFi channel runs them on Friday night - but they are running the 3rd season now.