Parkour is actually different to freerunning. They are used interchangeably these days but there are actually distinct differences.
Parkour, also known as the "art of displacement" or "the martial art of running away" (which is funny since it was pionered by the French), is the act of getting from point A to point B as efficiently as possible.

Freerunning is pretty much just looking pretentious and tricky while you run around on things.

(Also fixed up the spelling in the title so that native English speakers don't get confused.)