The V-Ray Material Builder node is a container that allows you to create a variety of V-Ray materials. By default, it creates a BRDFVRayMtl connected to a V-Ray Material Output node. From here, a variety of V-Ray nodes can be created such as BRDF and utility material nodes, textures, mapping nodes, and atmospheric effects.
UI Path: ||mat Network|| > V-Ray > Material > V-Ray Material Builder