Shutter Speed - Why is it Important
Shutter speed is useful mainly to control how much motion to show in an image.
Shutter priority mode is usually marked with "S" or "Tv" on the camera.
Longer the Shutter is open, you would see more motion blur
Speed set to 1/1000th of a second will give you a fairly sharp image because shutter was open for a short period of time.
Speed set to 1/40th of a second will give you a blur image because shutter was open for a longer period of time allowing light to move freely in short time
Fast shutter speed will give more tention/drama/sharpness in the image
Slow shutter speed will give dreamy motion
With long/slow shutter speed shoot in low light to avoid over exposure.