why could i see IR light in a camera?
This isn't really an electrical engineering question, but the short answer is that your eye has limitations. All light is a subclass of a larger form of energy called electromagnetic radiation. 



You can't see EM radiation with a wavelength shorter than around 730 nanometers, or what our brains perceive as red. However, your camera doesn't have the same limits, and will pick up the infrared light and try to display it just like any other light.