Natural occurrence is a classification of the elements of the periodic table according to naturally existing stable, radioactive or only synthetically produced nuclides.
Primordial elements have at least one naturally occurring stable nuclide. They existed before human intervention in nature.
Elements exist independently of human intervention only through the radioactive decay of others. They do not have a stable nuclide.
Synthetic elements do not occur in nature. They must be produced under laboratory conditions and sometimes at great expense.