endorsement vs approval

endorsement and approval both are nouns.

Word	Noun	Adjective	Verb	Adverb
endorsement	Yes	No	No	No
approval	Yes	No	No	No

As nouns, approval is a hypernym of endorsement; that is, approval is a word with a broader meaning than endorsement:

Other hypernyms of endorsement include commendation.

endorsement (noun)	approval (noun)
the act of endorsing	the formal act of approving
formal and explicit approval	a message expressing a favorable opinion
a promotional statement (as found on the dust jackets of books)	a feeling of liking something or someone good
a speech seconding a motion	acceptance as satisfactory
a signature that validates something