Sealed cooktop and range burners have a smooth surface right up to the edge of the burner with no space or large openings for spills to drip underneath the cooktop. Sealed gas burners have a round ceramic cap surrounded by a ring of very small openings for the flames. Sealed electric burners are covered with a ceramic cap or sealed underneath a smooth ceramic cooktop.
Traditional open stove burners surround the heat source with an opening. A drip pan is provided to catch spills, but over boiling sometimes leads to spills dripping down underneath the cooktop. The drip pan is removable to clean in the sink, but the stove top needs to be lifted to clean underneath. With a sealed burner, spills simply land on the smooth the cooktop for easier cleanup.
Sealed burners hold pans closer to the heating source than open burners for faster overall heating and spread the heat more evenly across a pan's surface to reduce hot spots. On the other hand, open burners heat up faster than sealed burners and provide better airflow for gas flames. This minimizes the risk of the burner going out when heating a large pot over a low flame. Using a burner that closely matches the pan size helps minimize that risk on sealed burner units.