Maybe this question is needlessly elementary, but I can't help but ask - Is there any difference between потому and поэтому either in terms of definition or usage? They both tend to be translated most often as 'therefore,' but is there any noteworthy difference in definition between them or something to note when one word is chosen over the other (for example a stylistic difference)? Any information about their respective etymologies would be interesting as well.
Not an elementary question at all.
The difference is this: поэтому presents the consequence as the new and/or important part of the message, whereas потому focuses more on the cause ("and that was why..."). That focus is very often strengthened by the "emphatic" pre-verbal и:
На нём была куртка, поэтому я решил, что он зашёл с улицы.
"He was wearing a jacket, so I thought he'd come in from outside." [And that led to something later in the story, or is just an aside.]
На нём была куртка, потому я и решил, что он зашёл с улицы.
"He was wearing a jacket, and that's why I thought he'd come in from outside." ["Okay, I failed to spot a lurking criminal, but how was I supposed to know? He did put on a convincing act."]
In the second example, поэтому я и решил is also possible — and, in fact, more likely in the vernacular (where потому is rarely used outside of потому что, which is for all intents and purposes a different expression). But using потому always gives you a more explicit focus on the cause rather than the consequence.
As for the etymologies, they're very simple: the preposition по plus the dative of это and то, respectively. Here, по carries its older meaning of "after" or "following".
Probably, the most clear difference in usage is that "поэтому" always follows the already expressed reason for something, while "потому" (unless it's a part of undivided "потому что") can precede it as well. E.g. you can't use "поэтому" in this sentence:
Я потому так поступил, что это мне велел начальник.
But you can use either word in a sentence beginning with the explanation of reasons:
Начальник это мне велел, и потому я это сделал (= поэтому я так и сделал).