> Rendering is a term that can be understood on different levels of abstraction. Depending on the context, it has a slightly different meaning. In any case, ultimately it describes the process of generating an image.

Could we clear up more the meaning of rendering and how it optimizes the performance mentioned in the article? Suppose the DOM has not changed, is the DOM repainted? How about in the case you type into a textbox which expands this container, causing adjacent elements to cascade into a new position?

Is this something similar to how mobile devices do not have to render content that is "not" displayed on the screen, as in the example of a large ListView so the mobile device does not have to immediate render any content that is expected to be off screen.