quag vs peat bog

quag and peat bog both are nouns.

Word	Noun	Adjective	Verb	Adverb
quag	Yes	No	No	No
peat bog	Yes	No	No	No

As nouns, peat bog is a hypernym of quag; that is, peat bog is a word with a broader meaning than quag:

quag: a soft wet area of low-lying land that sinks underfoot
peat bog: wet spongy ground of decomposing vegetation; has poorer drainage than a swamp; soil is unfit for cultivation but can be cut and dried and used for fuel

Other hypernyms of quag include bog.

quag (noun)	peat bog (noun)
a soft wet area of low-lying land that sinks underfoot	wet spongy ground of decomposing vegetation; has poorer drainage than a swamp; soil is unfit for cultivation but can be cut and dried and used for fuel