What's commonly known as black light is actually
ultraviolet (
UV)
light. Typical
black light bulbs have a purple (i.e. violet) glow, since they emit both
UV as well as some
visible light.
Often used in clubs, bars and similar places. They make white shirts glow quite brightly, and teeth and fingernails too.
Trivia: The reason shirts glow so brightly under black light is that producers of laundry detergent add chemicals that glow under UV. This way, when one is outside, the natural UV from sunlight causes these chemicals to glow, making the shirt whiter than white.