Comparing to humans cats have much better night vision. Their eyes have more rods (low-light photoreceptors) and a reflective surface behind the retina that improves night vision by making the light go twice through the retina. This also explains why their eyes may glow in the dark. You just see the light reflected back. Their eyes also have cones (bright light sensors). As opposed to humans who have 3 types of cones cats only have 2. This means that cats are dichromatic. They can only see colors as people with the most common type of red/green color blindness. But they are unable to see the difference between red and green hues as vividly as most people. Even though the photoreceptors in their eyes can technically distinguish hues it is not entirely clear whether cats are interested in colors or whether their visual system is capable of determining colors. Cats can change the size of their elliptical pupil much faster than humans making it easier to adjust their vision between brighter and darker places.
What do they see?