Question

what is the relationship between shutter and Iso

Answer 1

Shutter speed measures how long the camera's shutter is open. ISO is a measurement of film speed, which is the sensitivity of the film and/or digital sensor.

Generally speaking, slower shutter speeds allow you to use a lower speed of film (which has a lower ISO number). The inverse is also true- keeping the shutter open for less time (faster shutter speed) reduces the amount of light reaching the film/sensor, so you have to use a higher sensitivity.