Animals, especially ones who are active at night, have a reflective surface behind their retinas. That surface is called a tapetum lucidum and it helps them see in the dark. Basically its job is to reflect light, like a mirror, in the eye to allow what little light there is at night to hit photoreceptors in the eye. Light passing into thetheir eyeballs bounces off from the tapetum lucidum, giving the animal the ability to reflect what little light is incoming, thus allowing it see in near darkness. Due to the reflection, their eye glow. Human eyes don't shine/glow because they don't have this layer of tapetum lucidum.