hot pad vs heating pad

hot pad and heating pad both are nouns.

Word	Noun	Adjective	Verb	Adverb
hot pad	Yes	No	No	No
heating pad	Yes	No	No	No

As nouns, hot pad and heating pad are synonyms defined as:

hot pad and heating pad: heater consisting of electrical heating elements contained in a flexible pad

hot pad (noun)	heating pad (noun)
heater consisting of electrical heating elements contained in a flexible pad	heater consisting of electrical heating elements contained in a flexible pad
a pad for use under a hot dish to protect a table