The is the default renderer. By default, you use the scanline renderer when you render a scene from the or from Video Post. The Material Editor also uses the scanline renderer to display materials and maps.
As the name implies, the scanline renderer renders the scene as a series of horizontal lines. 3ds Max additionally provides the interactive viewport renderer to provide a quick and simple rendered view of your scene as you work on it. You might also have other plug-in or third-party renderers that you've installed to work with 3ds Max.