Distinction
Sometimes a distinction is made between the reality — and all that we know or perceive of it, the (mental) representation of reality. But such a distinction, though sometimes making perfect sense, is far from being considered absolute.
On the one hand, every representation of reality is real by itself; on the other hand, all that we regard as real at some time, eventually turns out to be just a representation.
So this distinction plays an important role specifically in the advance of knowledge (which is always paired with practical changes, changed habits or so). In effect it is the distinction between good or bad representations, between those matching and forwarding reality — and those missing and blocking it.