Our clients frequently ask about the grain patterns (figures) in wood. The pic below explains how a log is milled:
For a light-hearted explanation, Stumpy Nubs, a woodworker, explains what a “Board Foot” measurement is.
Then there is grading of the wood itself: #1, #2, #3, etc. #1 is knot-free. #2 has a few knots. #3 has more knots, and so on.
There is much more to discuss on this topic.