Planing

Planing removes thin, controlled shavings from a board's face, either to bring it to a consistent thickness or to leave a smooth, finished surface. A hand plane does this with hand power and skill; a thickness planer does the same job by feeding the board through spinning cutterhead rollers, fast and repeatable across many boards. Either way, planing only follows a board's existing reference face -- it flattens nothing on its own, which is why jointing a true reference face usually has to come first.