Hank Green, from SciShow, invited Henry Reich, from Minute Physics, and they talked about a couple of things. Henry Reich is a physics professor with a talent for storytelling and filmmaking. His channel has great videos with insights in the world of science.
For example, even in the interview he explained that fluorecense is the process in which UV light is absorbed by electrons who jump on a higher energy level only to get back on their original level later on. When they get back into their level they emit light in visible spectrum. This process is done in mere nanoseconds.
Phosphorescense is a process that lasts longer in which the electrons that absorb regular light get back in their original level and emit green light.