get it vs get onto

get it and get onto both are verbs.

Word	Noun	Adjective	Verb	Adverb
get it	No	No	Yes	No
get onto	No	No	Yes	No

As verbs, get it and get onto are synonyms defined as:

Other synonyms of get it include catch on, cotton on, get wise, latch on, tumble, twig.

get it (verb)	get onto (verb)
understand, usually after some initial difficulty	understand, usually after some initial difficulty
receive punishment; be scolded or reprimanded