Lamination is a protective layer. It adds a thin film over the printed surface. This film changes how light interacts with the ink and paper.
On coated art card (250gsm Art Card, 310gsm Art Card, 360gsm Art Card), the paper already has a slight sheen. Lamination modifies this existing sheen. gloss lamination amplifies it. matt lamination and soft touch lamination suppress it.
On natural and texture stocks (360gsm Natural White, 400gsm Classic Black, 335gsm Kraft Card, 300gsm Auspicious Golden) the paper is supplied uncoated, and we do not laminate it as standard. Ink is absorbed into the fibres, so the colour dries deeper and more matte. That surface is the point of the stock, not something to cover.