There are two types of wood flooring on the market today. While both choices look and feel the same, there are some key differences between the two.
Solid hardwood flooring is milled from a single piece of wood then covered with a thin, protective finish. Having a single, solid wood plank allows the floor to be sanded and refinished, numerous times throughout the life of the floor. One drawback is the wear that humidity can put on this floor. If the relative humidity in your home isn't kept between 45% - 65%, warping will result from expansion and contraction. Solid wood is only to be installed in the floors above grade.
Engineered wood will look no different than solid wood, once it's installed. Keep in mind, they're both real hardwood floors- they are simply made using a different process. Engineered consists of multiple cross-stacked layers of plywood with a veneer on top. This composition is what allows the wood to remain unchanged by humidity. Making engineered wood far more durable and flexible.