Certain material expressions are parameters, meaning their values can be modified (dynamically during runtime in some cases) in a Material Instance of the base material containing the parameter. These expressions should be given unique names, via the Parameter Name property, to be used when identifying the specific parameter in the Material Instance. If two parameters of the same type have the same name in the same material, they will be assumed to be the same parameter. Changing the value of the parameter in the Material Instance would change the value of both the parameter expressions in the material. A default value for the parameter will also be set in the base material. This will be the value of the parameter in the Material Instance unless it is overridden and modified there.