Parkour is a philosophical art of movement (or as the French say, déplacement). The idea is to challenge your body and your mind to move as fast and precisely as you can, from balconies to lampposts to rooftops. Parkour allows for exercise and creative expression at the same time.
David Belle is the founder of the parkour movement. He spent time in the army and worked as a firefighter and a gymnastics coach. He and a group of friends who called themselves Yamakasi began to practice parkour. Belle joined the Troupes de Marine (the French marines), and though he excelled at obstacle courses, he left the military when he realized it would hold back his free spirit.
Belle and his friends continued to develop parkour and started filming themselves. The footage got around and directors began incorporating parkour into films and commercials.