LED bulbs are designed to replace incandescent or screw-in CFL bulbs, as well as candelabra or low-voltage MR16 bulbs. LED bulbs have a driver inside of their base. This driver is what determines if the bulb is dimmable, what dimmers can be used with the bulbs, and the bulb’s overall dimming performance.
LED fixtures come in a variety of different forms, from cove lights and downlights to pendants and troffers. The driver will either be mounted within the fixture housing or be a separate component mounted remotely from the LED source. You can usually choose from multiple driver options, depending on whether you need a dimmable or a non-dimmable fixture and depending on what type of dimmer you want to use with the LED fixture.