Luminescent things glow with light. The illuminated screens of your laptop and TV are both luminescent.
Things that glow in the dark, like the reflective safety strip on your dog's leash or the numbers on your alarm clock, are luminescent. Other luminescent things include light bulbs, the stars in the night sky, glow worms, and certain glowing jellyfish and other sea creatures. When a living thing is luminescent, it's a phenomenon called bioluminescence. The Latin root of both words is lumen, meaning "light."