I was reading a book of Mike Cohn called Agile Estimation and Planning, which btw is an excellent book! But since I am a lazy reader I though it might find a talk of Mike Cohn on Youtube that would also cover this topic, and yes I did

If you are interested in Agile estimation and planning you might want to checkout this video. It gives you a nice overview of the ideas behind agile planning and you`ll also learn some scrum terminology aswell.