What is ISO in camera option?
ISO controls the sensitivity of the camera to light.
Lower ISO means lower light sensitivity.
The higher the ISO number, the faster the shutter speed. It is best used in dark areas.
Note: Higher ISO settings may distort an image or may produce with photos with more noise.
ISO is one setting of the camera being considered together with the Aperture setting and shutter speed. You need to mix this three to capture the best image you desire.