This page shows the VRayMtl Presets, available in the Basic parameters rollout.
Overview
Presets use settings that work well (in terms of speed and realism) as a starting point or for general-use cases. However, when a custom scene requires it, the material parameters values can be further edited to work best. For example, Glass and Glass (Tinted) use glossiness values that speed up rendering, but rendering a close-up view of a realistic glass object may require further adjustments. For an in-depth approach refer to the How-To tutorials.
Non-realistic material presets, such as Chocolate, Plastic, Ceramic, and Rubber are ‘quick’ compared to their realistic (SSS-enabled) counterparts. They can be used for generic plastic for the plastic backs of computer monitors or laptops in a meeting room, or for the car tires in a scene where the cars are somewhere in the distance, etc.