The window regulator mechanism is the device which allows the person sitting in the car to open and close the window next to them.
Concealed behind the door panel, the window regulator mechanism is either manual or electric. Manual window regulator mechanisms are operated by a handle on the side panel of the door beneath the window. This handle is connected to the winder mechanism, and when the handle is turned by hand this causes the window regulator mechanism to wind or unwind the window accordingly, with the rotation of the handle. When the handle is turned the cable it's connected to is wound around a spool attached to a gear mechanism which winds the window up or down. Electric window regulator mechanisms are powered by a motor which is activated by a switch within easy reach of the driver, usually found on the dashboard, arm rest or door panel. All electric windows in the car can be controlled by the driver's controls but individual windows will usually have a switch to operate them individually too. The glass in car windows is held in place when the window opens or closes by track assemblies which assists with the smooth operation of the window.
If the window regulator mechanism is damaged the mechanism won't work properly and the window will move slowly and judder, or simply stop working and get jammed open or shut. When buying a replacement window regulator mechanism it is important to make sure you choose the right window regulator mechanism so it will fit the make and model of your car.