The most common wood flooring consists of solid, one piece boards, usually nailed to a subfloor of wood. This wood flooring consists of two or more layers of wood laminated together. On the top, the wear layer is usually a hardwood veneer of varying thickness, with the lower layer being a softwood backing. It also can be glued directly to a concrete slab. Unfinished floors, installed on-site, give you many choices for colorations and durability.
Most solid flooring is unfinished while most engineered flooring is pre-finished.