CBV stands for Compressor Bypass Valve. This device is responsible for releasing boost pressure from the system when you let off the throttle. This will prevent compressor surge and help keep your turbo running properly. Please note that this is NOT a wastegate and the wastegate upgrade add-on is not required.
A wastegate is a device that is used to control boost pressure. This is the device responsible for regulating the actual boost output. Please note that the wastegate upgrade add-on is required in order to use this device properly.