How a floorboard has been sawed from the log has bearing on its appearance, cost, and performance.
Quartersawn boards have a straight grain pattern. The milling process takes longer and results in more waste, so quartersawn boards are more expensive. But they are extremely stable and wear evenly.
Plainsawn boards have a wavy grain pattern. They are more common than quartersawn boards. However, in humid regions, gaps can develop between boards, because they expand and contract from side to side.