Windlass
A Windlass (anchor windlass) is the heavy machine mounted on the forecastle that raises and lowers the anchors. Its cable lifter (gypsy) engages the links of the anchor chain to heave in the anchor, while a brake and a bow stopper hold the cable when the anchor is stowed or the ship is riding at anchor.
Most windlasses also carry warping ends or drums to handle the forward mooring lines. Windlass design and holding power are set by classification rules according to the size of the anchor and cable, because the machine must be able to weigh anchor and to hold the ship at anchor in a blow.
The windlass is what lets a ship anchor safely and recover its anchor, and it holds the ship when riding at anchor. If it cannot heave the anchor or its brake will not hold the cable, the ship loses a fundamental means of stopping and holding position, so its rating and maintenance are closely regulated.
What is the difference between a windlass and a capstan?
A windlass is the horizontal-axis anchor machine on the forecastle with a chain cable lifter; a capstan is a vertical-axis barrel for heaving lines. Windlasses handle the anchor cable; capstans and winches handle mooring lines.