The defrost thermostat / bi-metal protector is a thermal cut-off that will break connection to the heater if the unit becomes too warm. These are typically a thermostat of last resort, so if continuity dies, the heater is rendered totally inoperable, and a new unit needs purchased before the heater can run again properly.
DA47-00243K contains one harness and a longer length from the harness connector to the thermostat.
My Samsung refrigerator has been plagued with freezing up for the last couple of years. The freezer section working normally but the fridge icing up. The secondary heater around the fan area certainly seems to be working. Ben was certainly responsive in answering all my questions.