The most common electroluminescent (EL) devices are composed of either powder (primarily used in lighting applications) or thin films for information displays (Wikipedia).
To put it simply, EL lamps or "high field electroluminescent" lamps use electric current directly through a phosphor to make light. Unlike most lamps, they can be shaped to be extremely flat, or in narrow wire-like shapes. Electroluminescence or "EL" is the non-thermal conversion of electrical energy into light energy. This phenomenon is used in EL lamps, LEDs, and OLEDs (edisontechcenter)
In the field of paper and book restoration and conservation
EL is a sheet of thin and flexible plastic coated with EL material so it is like one big glowing square. It emits an even aqua glow over the entire shape and creates no heat, which makes it suitable to be used instead of the light table during paper restoration and conservation process, since it is a thin sheet, so that it can be easily used for paper mending in books without any needs to disbanding the binding.