This photo was shot with a small aperture (f/16), you can see that the buildings behind are still fairly sharp.
This photo was shot with a large aperture (f/1.4), the depth of field is very shallow
We used a lower ISO for this photo, you can see there is minimal noise.
For this photo, the ISO is set extremely high, you can see there is a lot of digital noise.
Using a slow shutter speed allows us to blur movement.
Using a fast shutter speed allows us to freeze movement