There are over 50 species of hardwood used in the flooring market today, choices ranging from Red Oak to Tigerwood.  Each species varies from open to closed grain patterns and many different colors.
Also, each has its own side hardness, otherwise known as Janka hardness (shown below).  
      Staining  wood, generally red or white oak, allows you the freedom to coordinate the decor of your home and really bring out the look you want.  The color range of the stains available today is literally limited only by your imagination.
    

                                                                          Exotic and Domestic Species Images

     The Janka hardness rating represents the resistance of wood to wear, marring and denting.  The higher the rating, the harder the species.  Wood flooring is a natural material and will dent, mar, and wear, this rating is merely a guide for comparing various species.   The most commonly used wood species are Red and White Oak, Hickory, Cherry, Pine, and Walnut.