Traffic lights, traffic signals, or stoplights are signaling devices positioned at road intersections, pedestrian crossings, and other locations to control the flow of traffic. Traffic lights normally consist of three signals, transmitting meaningful information to road users through colors and symbols, including arrows and bicycles. The regular traffic light colors are red, yellow (also known as amber), and green, arranged vertically or horizontally in that order. Green at the bottom. Although this is internationally standardized, variations exist on national and local scales.

Source: Wikipedia