I apologize if this has already been explained, I've searched both here and elsewhere online and can't find a clarification.
So far as I understand, both "che" and "quel" can mean "that" but they do not seem to be interchangeable.
Is "che" abstract while "quel/quella/etc." is concrete?
The example where I encountered this confusion was while trying to clarify if something I'd said was weird by asking (in Italian) "is that a strange thing to say?" In trying to find which form of "quel" would be appropriate (since I wasn't sure on the gender of the noun) I was told that none were and I should use "che." This is the entirety of what my guess is based on, I've really struggled to find any resource on this at all.