Rod photoreceptors and rod-connected nerve cells through the retina are responsible for pathways concerned with night vision and increased sensitivity of our visual system under what is called scotopic conditions (conditions of very little ambient light). Most vertebrates have a preponderance of rod photoreceptors in their retinas and such animals are very good at hunting and movement at night because of their very sensitive scotopic visual systems. Some animals are even completely nocturnal and have lost some of their cone types and their cone system neurons.
Humans, of course, are highly visual vertebrates and function mostly with their cone systems for color and high acuity form vision. However, the rod system is also important for our capacity to move around and function in scotopic conditions. If our rods or rod system neurons become diseased and degenerated we become night blind as happens to unfortunate people who have a disease called retinitis pigmentosa.
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