high relief vs embossment

high relief and embossment both are nouns.

Word	Noun	Adjective	Verb	Adverb
high relief	Yes	No	No	No
embossment	Yes	No	No	No

As nouns, embossment is a hypernym of high relief; that is, embossment is a word with a broader meaning than high relief:

high relief: a sculptural relief in which forms extend out from the background to at least half their depth
embossment: sculpture consisting of shapes carved on a surface so as to stand out from the surrounding background

Other hypernyms of high relief include relief, relievo, rilievo, sculptural relief.

high relief (noun)	embossment (noun)
a sculptural relief in which forms extend out from the background to at least half their depth	sculpture consisting of shapes carved on a surface so as to stand out from the surrounding background
	an impression produced by pressure or printing