Concerning the lamp(s) inside this product and spare part lamps sold separately:
These lamps are intended to withstand extreme physical conditions in household appliances, such as temperature, vibration, humidity, or are intended to signal information about the operational status of the appliance. They are not intended to be used in other applications and are not suitable for household room illumination.
This nut is situated between the salt container cover and seal within your dishwasher. If you have broken the salt container nut ring, this replacement part might be just the part you need to get your appliance working like new again.