"Normal wear and tear" is an often used phrase for which there is no "specific" definition, though the word "damage" is quite clear. It would make sense therefore to conclude - that without damage - is the definition of normal wear and tear - but of course life isn't that simple.
If you're unhappy with the amount returned of your security deposit, speak up! Call the property manager or owner. If still left wanting contact the BBB or use small claims court.
Here is information relative to Oregon, the zip code you listed: