The arrangement of gears seen above is named a worm and worm wheel. The worm, which in this example is definitely brown in colour, only has one tooth but it is like a screw thread. The worm wheel, coloured yellowish, is like a standard gear wheel or spur equipment. The worm always 
drives the worm wheel circular, it is never the opposite way worm gear and worm wheel circular as the system will lock and jam