Luminescence

Usually, light is obtained by heating solids or solid particles to high temperatures. By heating a tungsten(W), platinum wire or carbon filament electrically or in a flame, bright light can be obtained.
The phenomenon in which thermal energy is converted into the light is known as 'incandescence'.
When the emission of visible radiation occurs due to some cause other than temperature, the phenomenon is known as 'Luminescence'.
Light is produced at low temperatures, so it is also known as cold light.
In both incandescence and luminescence, light is emitted due to the return of electrons from the exciting position to a lesser excitation position or ground state. 

Classification of Luminescence

1. Photoluminenscence : 

Luminescence caused by light is called photoluminescence.
Photoluminescence that stops immediately as soon as the incident light is cut off is called fluorescence. Photoluminescence that continues for an appreciable time even after the incident light is cut off, is known as phosphorescence.

2. Chemiluminescence:

Luminescence resulting from chemical reactions is known as chemiluminescence.

3. Cathodoluminescence:

Luminescence caused by the bombardment of electrons is known as cathodoluminescence.

4. Electroluminescence:

Luminescence resulting from the application of an electric field to matter is known as electroluminescence.