lecturer vs talker

lecturer and talker both are nouns.

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

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

lecturer: someone who lectures professionally
talker: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of lecturer include speaker, utterer, verbaliser, verbalizer.

lecturer (noun)	talker (noun)
someone who lectures professionally	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)
a public lecturer at certain universities