one typo, above, Corrected version (the word in all caps below is the correction from the previous version):
"Just as a hot water heater is the terminology used to differentiate it from boilers, which also heat hot water but do so for the purpose of heating rooms rather than heating water for use as hot water, so too the hot water heater is not referred to as a "tank" because there are in fact tanks used in commercial settings that do not heat the water, but only store the hot water that was heated by the hot water HEATER.
In summary, there are water heaters that do not heat water for the purpose of usable hot water to be consumed (i.e.: boilers). Therefore, the term hot water heater is used to differentiate it from boilers.
There are tanks that store hot water, so the term hot water heater is used to differentiate it from the tank, which merely stores the hot water but doesn't heat it"