The show has been running since 1963, albeit with a 12 year gap when it was off the air (although it did continue in audio adventure form, which are considered canon).
Since coming back to the small screen in 2005 it has enjoyed enormous success. However, with season 11 recently starting, it can hard for newcomers late to the party to know where to begin in order to get the full flavour and general gist of the show.
Check out this video that offers suggestion for the 10 best episode of Doctor Who for newbies.