Using ISO 400
Aperture
refers on how much light a camera can let in at a given shutter speed. Aperture also affects the distances that appear to be in focus when a picture is taken. This is called depth of field (DOF).
Shutter Speed
Shutter speed is the duration for which a camera can record light to take a single picture. The shutter speeds of a camera are described as a range measured in seconds and fractions of a second
Note:
fast shutter - speed gives a camera the ability to capture objects in motion and good pictures in every bright light
slow shutter - gives camera the ability to capture detailed pictures in low light
ISO
defines how film sensitivities are measured
It refers to equivalent sensitivity.
Note: A higher ISO rating means more sensitivity to light but produces pictures with more noise which is similar to pattern of film grain.