agoraphobia vs phobia

agoraphobia and phobia both are nouns.

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

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

agoraphobia: a morbid fear of open spaces (as fear of being caught alone in some public place)
phobia: an anxiety disorder characterized by extreme and irrational fear of simple things or social situations

Other hypernyms of agoraphobia include phobic disorder, phobic neurosis.

agoraphobia (noun)	phobia (noun)
a morbid fear of open spaces (as fear of being caught alone in some public place)	an anxiety disorder characterized by extreme and irrational fear of simple things or social situations