Electroluminescence (EL) is a phosphorus ink that gets printed on paper, sandwiched between conductive material and then charged with AC or DC power. When that happens it creates a flat and cool light with numerous applications. when the ink is printed in small segments and controlled with a programmed circuit board you can light in sequence, creating an animated lightsource - and that's when it gets interesting! Because of it's compelling look, companies use it to advertise their product and promote their brand. It is often compared to neon but with far superiority because of it is:

Flat
Non-toxic ("Green / Eco-Friendly)"
Low Power Consumption (80% less)
Longer Life Span (5X that of Neon)
Design Flexibility
Creative Incorporation to Posters & Displays