What looks like a simple (or spooky) reflection is due to a special layer of tissue that cats and many other animals have behind the retina of their eyes. This special layer of tissue is called the tapetum lucidum and it reflects light that wasn't absorbed by the retina back into the eye so that it has another chance to be absorbed and send a signal to the brain.
Because of the tapetum lucidum, cat's are about 6 times more senstive to light than humans. This allows cats to see so very well in dim light, which is great for those late-night mouse (or toy) hunts.
When light hits the tapetum lucidum just right, it is reflected back out the front of the eye and we see that as eye shine. Most cats eyes shine green, but Siamese cats eyes shine red.
Since humans don't have a tapetum lucidum, our eyes don't shine.
Note: my cats are not harmed by the occasional flash that catches their eyes, but please don't torment your cat or any other animal by shining bright light into their eyes. And don't shine bright lights into nocturnal animals eyes like a hamster. Their eyes are designed for vision during darkness (night) and bright light can cause damage to their vision.
The Saturday Blog Hop themed "Reflect" starts here.