Setting difference... Is there a difference??

[RichardTaylor]

You up the ISO (if you keep the aperture the same and increase the shutter speed) to make the sensor more sensitive to light..

The bottom line is.

(1) The sensor needs a fixed amount of light of light for a technically correct exposure..

How much light it needs is controlled by the ISO (sensitivity)

(2) How much light it gets is controlled by
The aperture (how much light at once)
and
The shutter speed (for how long)