This graphic is a good explanation of light.
What is a “stop” or “f/stop?”
A “stop” means “a factor of two” in light intensity. So when it says a digital sensor can sense a range of brightness of 14 stops, it means that the brightest part of the picture is no more than 214 = about 16 thousand times brighter than the darkest part of the picture.
Put another way, if you were using the spot metering feature of the camera and you were to measure the brightest and darkest parts of your scene, and the brightest part reads 1/1,000th of a second, then the darkest part must read no less than 8 seconds (14 stops away) for everything to be visible.