PL lamp means Plug in - Light Bulb, the most comment application in CFL(Compact Fluorescent Lamp) which require assistance components to make it work or light it up, different to incandescent light bulb, it can light up by just itself direct connect to our home dlectricity ac 100V to 240V.PL lamp is simply connected to the pins at the base. External ballasts must be used to supply the high voltage necessary to start the lamps.