What is a Panel?
A panel is a set of images, usually 1 to 3, of a single action, seen from one or more perspectives. For example 14.21 Dragon Sleeper and a Stomp is a panel that contains 3 images.
The number at beside the panel describes the chapter and the number of that panel. In this case, this panel is from Chapter 14 and is the 21st panel of that chapter. If the panel has a b prefix, like b10.20, this means that chapter is from the Behind the Scenes catalog.
What is a Post?
A post is an story update that can contains one or more panels. For example 20.29 to 20.33 Final Humiliation is a post that contains 5 panels.