Shutter-priority describes a metering method which automatically sets (or displays) the lens aperture, based on the shutter speed chosen by the user. The term typically refers to a camera offering autoexposure—for example, one where an A or EE position is found on the f-stop ring. But shutter priority could also describe a method of manual exposure metering.
Shutter Priority may be be the preferred type of metering when the photographer needs to control the amount of motion blur in a photograph. A slow shutter speed will blur moving subjects, whereas a high speed will stop action and reduce the effect of camera shake, rendering a sharper image.
(Compare with Aperture priority.)