What do you mean by photo exposure? What are the characteristics of exposure? What if the speed is extremely fast?

Photo exposure is to make light properly shine on the image sensor of photographic film or digital camera to form an image that is basically consistent with the color, brightness and contrast of the object being photographed. If the shutter speed is fast, the aperture will be opened, otherwise it will be underexposed, but if it is too fast, there may be no suitable aperture to match it, and the photo will become waste.