Here's an example of the Stop with a photograph.
Let's say this picture was taken at f/8.
To vary the exposure. we'll be changing the lens opening.
The shutter speed will remain constant at 1/250th.
The exposure on the next photograph was changed by one stop: f/8 to f/5.6.
The amount of light has doubled.
The photograph is brighter—by one stop.
Here's the first photograph again, taken at f/8.
The exposure on the next photograph was also changed by one stop: f/8 to f/11.
The amount of light was halved.
The photograph is darker—by one stop.
Now let's look at how Stop is "spoken" by three countries on your camera.