Parkour is French. Originally invented by the French Military, it was used for getting from point A - B efficiently. Parkour is derived from its given French name: Le'Parkour. It is not actually described as a sport but more like an artform, just like cardistry or magic.
There is a difference between Parkour and Freerunning. Parkour is, like I said before; getting from point A - B efficiently. Freerunning is the same but incorporates flips and crazy stunts into the actual parkour itself.
How does he know all this?
My best friend and J&T colleague Reuben, does Parkour/Freerunning, Gymnastics and Breakdancing as well as Cardistry and Magic.
Here is a video for an SNC entry he entered:
http://www.youtube.com/watch?v=wuXgpzQsZXs&feature=youtube_gdata_player