Rinse aid is a liquid product used in dishwashers to improve drying and prevent water spots on dishes. It works by reducing the surface tension of water, allowing it to flow off dishes more easily. This helps to ensure that dishes come out clean and dry after a wash cycle. Typically, rinse aid is dispensed automatically during the rinse cycle of the dishwasher. It is especially useful for glassware and plastic items, which can often show streaks or spots if not treated. Many brands of rinse aid are available, and they can be found in most grocery stores alongside other dishwasher supplies like dishwashing detergent.