There are two main types of hardwood flooring: Solid and engineered. Solid wood floors are, as you might assume, one solid piece all the way through. Engineered, on the other hand, has only a top veneer that is real wood, attached to a backing that is not. Engineered wood is better suited for those areas where solid wood cannot be placed, such as in basements and below grade areas.
In making the solid wood choice, the most important aspect to consider is the species. Just like carpet fibers, each wood species has a different set of characteristics that can make one better suited for your home than others are. For instance, if your home experiences a great deal of traffic, you would be better suited to a wood that is very hard, such as oak, or an exotic species. Exotics are usually much harder than domestic species. Softer species are better suited for areas like closets and bedrooms, that have less foot traffic.