The difference between F5.6 and F11 is in a nutshell the size of the opening in the aperture to allow the amount of light into the camera and onto the film. The F11 is four times smaller than F5.6. Each step is 1/2 of the previous.
F1.4, F2, F2.8, F4, F5.6, F8, F11, F16, F32, F45, etc......
So...