enigma vs problem

enigma and problem both are nouns.

Word	Noun	Adjective	Verb	Adverb
enigma	Yes	No	No	No
problem	Yes	No	No	No

As nouns, problem is a hypernym of enigma; that is, problem is a word with a broader meaning than enigma:

enigma (noun)	problem (noun)
something that baffles understanding and cannot be explained	a source of difficulty
a difficult problem	a question raised for consideration or solution
	a state of difficulty that needs to be resolved