A literal response is what you see.
Something that can be provin
Yes. Literal is an adjective. It means "word for word," or the simplest form of something.
Literals are the values assigned to variables. int num = 10; Here 10 is the interger literal.
There is no literal idiom -- an idiom is a phrase that seems to mean one thing but actually means something else. The word "literal" means to take the words exactly as they seem to be.