Light Cone Explanation Not sure if this question belongs here, or on Physics. Would someone please describe the "anatomy" of a light cone and provide an intuitive example?

I have read the Wikipedia article (http://en.wikipedia.org/wiki/Light_cone) and I think I have a basic grasp of the concept. However, I still have questions: is a cone emitted every time there is a disturbance in the electromagnetic spectrum? Does every electron changing energy states emit a light cone? I understand the "future" light cone (I think). However, what of the "past" light cone? Is that what is observed when detecting redshifts?

Thank you for your answers/comments. They have helped my understanding of the light cone concept.
Think of dropping a pebble into a pond, and the circular pattern the resulting wave makes. Now take a photo every second, and stack these one on top of another, and you have a "cone" of sounds waves. The oldest image of the wave is also the biggest, and furthest back in time.