simple phobia vs phobia

simple phobia and phobia both are nouns.

Word	Noun	Adjective	Verb	Adverb
simple phobia	Yes	No	No	No
phobia	Yes	No	No	No

As nouns, phobia is a hypernym of simple phobia; that is, phobia is a word with a broader meaning than simple phobia:

simple phobia: any phobia (other than agoraphobia) associated with relatively simple well-defined stimuli
phobia: an anxiety disorder characterized by extreme and irrational fear of simple things or social situations

Other hypernyms of simple phobia include phobic disorder, phobic neurosis.

simple phobia (noun)	phobia (noun)
any phobia (other than agoraphobia) associated with relatively simple well-defined stimuli	an anxiety disorder characterized by extreme and irrational fear of simple things or social situations