line of descent vs folk

line of descent and folk both are nouns.

Word	Noun	Adjective	Verb	Adverb
line of descent	Yes	No	No	No
folk	Yes	No	No	No

As nouns, folk is a hyponym of line of descent; that is, folk is a word with a more specific, narrower meaning than line of descent:

Other hyponyms of line of descent include family, family line, kinfolk, kinsfolk, phratry, sept, side, breed line.

line of descent (noun)	folk (noun)
the hereditary derivation of an individual	the traditional and typically anonymous music that is an expression of the life of people in a community
the kinship relation between an individual and the individual's progenitors	people in general (often used in the plural)
	a social division of (usually preliterate) people
	people descended from a common ancestor