They can be refinished several times, which adds to their long life in your home. However, they are sensitive to moisture and are not recommended for installation below ground level, or directly over a concrete slab.
The Clear type of Oak has no visual blemishes or knots and is quite expensive. While the Select and Better qualities have some small knots and little dark graining.
They also have several wood plies glued together in which the core is generally a softer wood material and a hardwood finish layer is glued on the top.
They are easy to replace and come in a variety of domestic and exotic hardwood species.