system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 - How does glow in the dark work?

I've lived on this planet for 28 years and have never questioned it, as I assumed it was magic that was beyond my abilities to comprehend.
My eight-year-old asked me about it today. Give me an answer.
gpt
Normally when substances absorb the energy of photons they emit them back as light almost immediately. However some substances absorb the photons of light so that the energy of the photon kind of get's stuck into a "quantum traffic jam" within the molecules. It takes some time for the energy to be released as light from the "quantum traffic jam". This time is so long that when you turn off the lights, the light that was absorbed by the substance is emitted back with a delay.

You can maybe think if it like how metal and heat insulating material react differently to heat. If you point a torch to a heat insulation, you can almost immediately touch it afterwards, as it does not really contain heat that well. But metal on the other hand absorbs the heat for some time and you can still feel how it is hot after some time.