The coolant used for refrigerator evaporator coils is simply called refrigerant. It is used to move heat from one area to another and changes its state when entering the evaporator, moving from a liquid to a vapor form.
The refrigerant used in the coils is typically between 40 and 50 degrees Fahrenheit when it enters the evaporator. It absorbs heat without changing its own temperature, changing state at this time. While passing over the cool coil, the refrigerant may release heat and some moisture may condense, while the cooler and drier room air recirculates into the space needing to be cooled via blower.