GU10 refers to the type of base that MR16 bulbs have. These bulbs are commonly found in commercial spaces where a bright directional light is needed. A MR16 bulb is a Multifaceted Reflector bulb that has a reflective coating on the outside of the bulb and are used more commonly in retail spaces. Read more about the different types of MR16 and other LED bulbs with our blog Light Bulb Fitting Guide: Light Bulb Bases and Bulb Socket Types.