ISO

aperture: 3.5

shutter speed: 1/60

iso: 100

aperture: 3.5

shutter speed: 1/50 

iso: 6400

What is ISO?  The level of sensitivity of your camera to available light.

How does ISO work technically?With increased sensitivity, the camera sensor can capture images in low-light environments without having to use a flash. But higher sensitivity comes at an expense – it adds grain to the pictures.

in the picture?  the lower ISO makes the picture less blurry but the higher ISO(6400) makes the picture more grainy.

IN the exposure triangle?  The Aperture stays the same as the iso and the shutter speed change.