learner vs memorizer

learner and memorizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
learner	Yes	No	No	No
memorizer	Yes	No	No	No

As nouns, memorizer is a hyponym of learner; that is, memorizer is a word with a more specific, narrower meaning than learner:

learner: someone (especially a child) who learns (as from a teacher) or takes up knowledge or beliefs
memorizer: a person who learns by rote

Other hyponyms of learner include memoriser, quick study, sponge, dweeb, grind, nerd, swot, wonk, tutee.

learner (noun)	memorizer (noun)
someone (especially a child) who learns (as from a teacher) or takes up knowledge or beliefs	a person who learns by rote
works for an expert to learn a trade