What is the difference in the US between a stop sign and a traffic light?

A stop sign is a red, eight-sided metal sign that requires a driver to stop and then proceed when it is safe to do so. Many intersections have either two or four stop signs. When more than one car arrives at the intersection, the car that arrived first has the right of way. If more than one car arrives at the same time, then the car to the right has the right of way. An electric traffic light typically has three different signals: red indicates drivers should stop until the light changes; a yellow light indicates that the driver should stop if it is safe to do so because the signal is changing from red to green; and a green light means that drivers may proceed through the intersection without stopping.