Can you quickly explain "everything is impermanent"

Can you quickly explain "everything is impermanent"? Is it metaphysical or ontological claim, that nothing that "exists" will exist forever? Or is it a claim that nothing can always be (meaning having that nature, rather than 'exist') anything? If not that latter, does Buddhism universally agree that there is no *awareness* of something being what it is, without existence? ---------- Can I be aware of, for example, a shape being red without existence and "permanently" in the standard way of using that word, even if "everything is impermanent"?