As I said, basically it is an USB ↔ RS-422/RS-485 converter board. It can be used to communicate devices with RS-422/RS-485 interface by using a USB port of PC. Also, ground of USB port is isolated from ground of RS-422/RS-485 channel. It may help you to prevent ground loops in large systems. If you are not sure whether you need isolation or not, probably you do not need it.