self-knowledge vs understanding

self-knowledge and understanding both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-knowledge	Yes	No	No	No
understanding	Yes	Yes	No	No

As nouns, understanding is a hypernym of self-knowledge; that is, understanding is a word with a broader meaning than self-knowledge:

Other hypernyms of self-knowledge include apprehension, discernment, savvy.

self-knowledge (noun)	understanding (noun)
an understanding of yourself and your goals and abilities	the capacity for rational thought or inference or discrimination
	the cognitive condition of someone who understands
	an inclination to support or be loyal to or to agree with an opinion
	the statement (oral or written) of an exchange of promises

self-knowledge (adjective)	understanding (adjective)
	characterized by understanding based on comprehension and discernment and empathy