This page gives an overview of V-Ray's utility render elements and how they are used. Utility elements have a wide variety of uses both inside and outside of the compositing process.
Overview
The Utility Render Elements are a group of render elements that are generated for use in a number of different compositing and image manipulation needs.
Some of these render elements are also useful for optimizing renders and troubleshooting issues and aren't necessarily used as images in actual compositing.
Utility Render Elements List
Coverage - For each pixel, the final values for the render element are taken from the object that makes the largest contribution to that pixel.