In my experience, one of the toughest concepts for new WordPress developers to grasp is the difference in actions and filters.
By this, I don’t mean that they are difficult to use. In fact, I think most developers have a pretty easy time picking up how to hook their functions into hooks and filters when needed, but it seems as if its a bit challenging to grasp WordPress page life cycle and how actions and filters fit into the overall context of WordPress.
So in my latest article at Envato, I try to provide a clear understanding of WordPress Actions and Filters.