"Те" means "that" as an adjective-pronoun (tell me the real linguistic term) for neuter nouns. As in, going together with "той" and "та". E.g. те сонце = that sun
However, the equivalent of "that" in terms of noun-pronoun (again, my term) would be not "те" but "то". Going together with "це". E.g. Що це таке? = What is this? Що то таке? = What is that? Це моя чашка, а то — твоя. = This is my cup and that [one] is yours.
I'd say it's used a bit more rarely, but only because we talk more about things that are close to us xD If it is really something far and I'm pointing I would seldom say "це", that thing over there is definitely "то".
I think the terms are demonstrative adjective vs. demonstrative pronoun [https://en.wikipedia.org/wiki/Demonstrative where you get the fancy term "deictic" as a sort of bonus :) ]
I wouldn't have guessed it was the adjective version here! [although maybe I should have, "ты знала об этом" being perfectly natural Russian]
Just to double check, I take it you wouldn't say "Ти знала то?" either, right?
Wow, really good point.
"Did you know about this/that?" --> Ти знала про це? Really seldom "Ти знала про те?".
"Did you know this/that?" --> Ти це знала? I would prefer this word order. Virtually never "Ти те знала", a bit strange.
In English "this" and "that" sound natural, but for us I guess the logic is, if you're talking about it, it's a this, cause it's here in our discussion, and not somewhere there xD
P.S. Really cool I'm realizing only now that in Russian there's basically only "это" for this type of sentences! Even if the thing is far from you, you still say "Что это такое?" and not "Что то такое?" Nice :)