The Fibaro Bypass 2 is placed between the Fibaro Dimmer 2 and your fixture including dimmable LED lamp. Thanks to the bypass, the consumption of your LED lamp is limited to the minimum and dim your LED lamps with a minimum amount of wattage. Without a bypass, the chances are that your dimmable lamps start to flash when they get too little energy. The bypass prevents blinking and makes the dimmable LED lights shine under a minimum amount of wattage without blinking.
Note: the bypass only works in combination with the Fibaro Dimmer 2 and a dimmable LED lamp.