Override settings are global parameters that supersede or replace other individual settings in other parts of the V-Ray user interface. This is useful for making temporary changes on a scene-wide basis, which is useful for diagnosing scenes as well as refining and finding optimizations. For instance, you are able to toggle on or off all displacements in the scene without needing to address each displaced material/object individually.

Overrides are divided into sections for easy access as shown in the menu listing on the left.

 UI Path: ||Render Settings window|| > Overrides tab