Differentiate between rod and cone cells.

Rods are the rod-shaped cells present in the retina of an eye which are sensitive to dim light.
Cones, on the other hand, are the cone-shaped cells present in the retina of the eye which are sensitive to bright light.

However, cones are most sensitive to one of three different colours (green, red or blue). Signals from the cones are sent to the brain which then translates these messages into the perception of colour.
Rods, on the other hand, do not sense colour. That's why we cannot see colour very well in dark places.