This is a slides about progressive enhancement. It doesn't answer what is progressive enhancement, instead it talks about how to do progressive enhancement in practice. Then you will know why you need to do progressive enhancement. In my mind PE is not a buzz word, actually it's the Web's way. We should rediscover what's right way to build web. If everything is in correct layer, this best practice called progressive enhancement. Then you got a robust system which can work in different environment and can be access by both human and computer.
Clipping is a handy way to collect important slides you want to go back to later.