guessing vs idea

guessing and idea both are nouns.

Word	Noun	Adjective	Verb	Adverb
guessing	Yes	No	No	No
idea	Yes	No	No	No

As nouns, idea is a hypernym of guessing; that is, idea is a word with a broader meaning than guessing:

Other hypernyms of guessing include approximation, estimate, estimation.

guessing (noun)	idea (noun)
an estimate based on little or no information	the content of cognition; the main thing you are thinking about
	your intention; what you intend to do
	an approximate calculation of quantity or degree or worth
	a personal view
	(music) melodic subject of a musical composition