The grades can have different names from different manufacturers, but most common are clear, select, common (#1 and #2), and rustic or tavern. This only applies to domestic hardwoods as exotics have they own unique rating system wherever they are manufactured. Clear is usually the most expensive as it has the least amount of visible characteristics such as knots or color variation. In the order I named them, each grade shows more of these characteristics ended at rustic or tavern which will have multiple visual characteristics. This can include knots, dark graining, and more.