informant vs talker

informant and talker both are nouns.

Word	Noun	Adjective	Verb	Adverb
informant	Yes	No	No	No
talker	Yes	No	No	No

As nouns, talker is a hypernym of informant; that is, talker is a word with a broader meaning than informant:

informant: someone who sees an event and reports what happened
talker: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of informant include beholder, observer, perceiver, percipient, speaker, utterer, verbaliser, verbalizer.

informant (noun)	talker (noun)
a person who supplies information	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)
someone who sees an event and reports what happened