A stained floor is one where a colouring agent has been applied to the wood to change or enhance its natural tone. The purpose of staining is purely aesthetic—it brings out the grain and gives the floor a custom look, from light oak to deep walnut shades. After staining, a protective finish (such as polyurethane) is applied on top to shield the surface from scratches, spills, and wear, preserving both the colour and the wood beneath.