Meteor Shower Show

What caused the meteor shower we watched on August 11 2012 (The Perseids Shower)?

"Comet Swift-Tuttle, whose debris creates the Perseids, is the largest object known to make repeated passes near Earth. Its nucleus is about 6 miles (9.7 kilometers) across, roughly equal to the object that wiped out the dinosaurs."  Space.com

The Pereseid Showers are the bits of left over debris that falls off the Comet Swift- Tutle!  

Meteors from the Perseid shower streak past stars above the Los Padres National Forest in Frazier Park, California August 12, 2009. Mario Anzuoni/REUTERS Orginal