When I look up choking, the internet tells me it's "the mechanical obstruction of the flow of air from the environment into the lungs. Choking prevents breathing ..."
But, that's no fun at all and it really doesn't get to the fundamental core of what makes choking so exciting for the BJJ practitioner/athlete. Choking is cool. You're grappling with your opponent (often teammate/friend/buddy), and you arrive at a point wherein you have the awesome ability to deny them access to breathing and can possibly kill them. And, then you let them go. It's brilliant! God, I love Jiu Jitsu.
John Machado is the youngest of the Machado brothers and a 6th degree black belt under Carlos Gracie Jr. He's accomplished a ton in BJJ and, in short, is one of the all time greats (he's also a close friend of Street Sports, our academy in So Cal).
Let's not waste any time. Clock chokes, although tricky to finish for the untrained, are deadly, classic chokes from your opponent's turtle. This is basic stuff you need to have down. Let's watch a master break it down.