Capstan
A Capstan is a machine with a vertical rotating drum (the barrel), powered by an electric or hydraulic motor below deck, used to heave in mooring lines and warps. Line is taken in several turns around the barrel; as it turns, friction hauls the line in while the crew tails the slack.
A capstan has a vertical axis, distinguishing it from a horizontal-axis winch. On many ships the mooring machinery combines capstans, mooring winches and the anchor windlass. Traditional capstans were turned by hand with capstan bars; modern ones are powered.
The capstan gives the crew mechanical power to heave heavy mooring lines and warps that could never be hauled by hand. Together with mooring winches it is core deck machinery, and its condition and safe operation are central to mooring-deck safety.
What is the difference between a capstan and a winch?
A capstan has a vertical rotating barrel and does not store the line on itself; a mooring winch has a horizontal drum that both hauls and stows the line. Both heave mooring lines under power.