observer vs commentator

observer and commentator both are nouns.

Word	Noun	Adjective	Verb	Adverb
observer	Yes	No	No	No
commentator	Yes	No	No	No

As nouns, observer and commentator are synonyms defined as:

observer and commentator: an expert who observes and comments on something

observer (noun)	commentator (noun)
a person who becomes aware (of things or events) through the senses	a writer who reports and analyzes events of the day
an expert who observes and comments on something	an expert who observes and comments on something