Accumulation and Stratified Tank in Energyplus

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Hello, I would like to know the difference in EnergyPlus between the objects: WaterHeater and ThermalStorage

I want to simulate an accumulation tank that provides always water at 19 degrees and I also want to simulate another tank (stratified in this case) with 10 and 8 degrees for hot and cold side respectively. Could you please help me. Thank you