The term "wood grain" refers to the visual texture and pattern that is seen on the surface of a piece of wood. It is created by the fibers in the tree bark, which grow in different directions as the tree grows. The appearance of wood grain can vary greatly depending on the type of wood, with some having more prominent or distinct patterns than others. Wood grain can also refer to the direction and orientation of these fibers when a piece of wood is cut for use in furniture, construction, or other applications.