A ballast is the part of a fluorescent lighting system that regulates current and provides enough voltage to the fixture so the bulbs light. It is a box, usually black or white in color, in the center of the fixture with wires of multiple colors coming from it.
When using LED products, it is best to disconnect the ballast from the circuit and wire the products directly to the power source, as LED products require much less energy to operate and can even be sensitive to excess energy. Many of our bulbs are not compatible with ballasts, and even the bulbs that are Ballast Compatible may still have issues with buzzing, flickering or general functionality when used with ballasts.
Disconnecting the ballast in your fixture when going LED will also cut down your energy bill. If a ballast is operational, it is still drawing extra power from your home and needlessly amplifying it into your LED bulbs!