Catchlight is the highlight of a light source reflected off the surface of the eye. This highlight adds depth and dimension to the eye and gives the eyes life in portrait photos.
Catchlight comes in all shapes and sizes, depending on the subject. For example, a large round umbrella reflector will produce a larger, more pronounced catchlight than a small portable electronic flash.
Many portrait photographers use a reflector placed in the lap of the subject or a similar position. This produces a larger catchlight in the lower half of the eye. Please see some different examples of catchlight below:
As catchlight gives life to the subject, on some of my images I removed the catchlight from the eyes to create more of a disturbing image and almost dead like.