The protagonist, for some obscure reason, emits light around him- or herself. Usually done as substitution of awareness or ability to pick up cues (silhouettes, sounds, sound occlusion, touch, and such) on what's near you in low light situations.
The first video game about Self-luminance was released on December 1996.
Common in top-down games where awareness of immediate surroundings is harder to deliver than in 1st or 3rd person games via other means. Such as lighting differences in the environment don't reveal silhouettes.