What is shutter speed
Shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open. You can think of the shutter in your camera as a bit like a window shutter, you open up the shutters to let light in through the window, and when you close the shutters, the light is cut off. When you open and then close the shutters, the room gets brighter for a brief period and then goes dark again.
That’s pretty much what a camera does on your SLR or mirrorless camera.
Play this 5 second video to see a slow shutter speed action