The second element in the exposure triangle is the “Shutter speed”

This aspect is measured by seconds – it could be a second, portion of a second or more than a second.
A second or more is written as 1″
A portion of a second is written 1/100 for example

Shutter speed controls 2 things.

-First is the quantity of light coming to the camera .. a slower shutter speed lets more light into the camera and vice versa.

-Second is motion .. what does this mean?
Simply it is showing the motion or freezing it.
Have a look on the two photos of “Tanoora” I took below nearly from the same place with everything fixed except for the shutter speed and aperture to compensate the light that will be affected by the change in the shutter speed.
In the one showing the motion the shutter speed number is bigger (a bit slow) – 1/20
While in the one that doesn’t show the motion the shutter speed is smaller (a bit faster) – 1/125

I put a photo that explains the whole picture and another very famous picture in this subject which is the paper flower rolling from air.

Anyone needs to understand it more, please tell me.