Catchlight
The reflection of a light source visible in a subject's eye.
In depth
A catchlight makes eyes read as alive rather than flat, and its shape tells the viewer what shape the light was — a square softbox, a round beauty dish, a ring flash's perfect circle. Conventionally one catchlight is placed at the ten or two o'clock position; multiple competing catchlights usually look artificial and are often retouched out.
Examples in practice
An octabox leaves a single round catchlight at two o'clock, giving the eye life without the ladder-shape of a gridded box.