Solid wood is just that – one piece that is milled from lumber. It comes in a variety of widths, from 2-1/4" to 5" wide. It also comes in different thicknesses: 3/4" is standard, but you can also find "thin profile" solid that is 5/16" thick.
Keep In Mind:
Moisture and extreme temperature changes can cause solid wood to shrink and expand, potentially causing gaps between boards during colder or dryer seasons.
5/16" thin profile solid wood can be installed directly over concrete; 3/4" can't.
All solid hardwood can be sanded and refinished if needed (required every 15-20 years).
All urethane coated floors can be recoated as needed to renew the surface of the floor. This is more economical than sanding and refinishing.