Use underlay, why?

Underlay helps keep your flooring warm.  A modern underlay can make a big difference when it comes to improving your home’s insulation and therefore improving its energy efficiency.

Underlay aids in moisture resistance. The bottom layer of laminate flooring is composed of melamine backer, which aids in moisture resistance. 

Underlay helps absorb any grit and minor slab deviations. A good quality underlay can make the simple act of walking on your floor more comfortable, just by providing a subtle cushioning effect.