Rendering in visual art and technical drawing means the process of creating, shading, and texturing of an image, especially a photorealistic one. It can also be used to describe the quality of execution of that process. This is synonymous with illustrating.
The emphasis of the term is on the correct reproduction of light-and-shadow and the surface properties of the depicted objects, not on the emotional impact, composition, or other more generic qualities. Unsurprisingly, most often it is used in relation to the more exacting, meticulous techniques like pencil or airbrush.