What are the different grades for dimensioal lumber. Specifically hem fir vs. doug fir?

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Moisture content. There are two moisture grades, printed on stamps as "S-Dry," which means the board has less than 19 percent water weight, and "S-Grn" (for green), which means the board has more than 19 percent water weight. If you use wet wood in a project, the lumber will shrink, causing unsightly gaps or squeaky floors. If you buy green lumber or dry lumber that has been left out in the weather, try to buy and store it ahead of time so the wood can lose moisture.
Species. Lumber associations have grouped many different softwood species into stamp categories that can contain one species or many. The most common in the northeastern United States are: Southern Pine, Spruce-Pine-Fir, Douglas Fir, or Hem-Fir. "Homeowners must know the species category because each one has different strength and structural properties," .
Lumber grade. There are many different types of lumber grades, most aimed at the construction industry. Most homeowners will see just four grades: Select Structural (SEL STR), No. 1, No. 2 and No. 3. Select structural is nearly knot-free and, as a result, is rare and very expensive, Select grades are typically used if appearance is important. Grades 1 through 3 are graded on how many knots appear in the board and how that affects the strength of the lumber.