Question

What is a light made of ?

Answer 1

Light is a form of energy and it is made up of packet of rays or a bundle of rays.

Answer 2

Light is what's called an "electromagnetic wave", just like radio waves, microwaves, X-ray waves, etc. Electromagnetic waves typically start when an electric charge jiggles back and forth. 

Depending on the "frequency" of the electromagnetic wave (or how scrunched together the peaks in the wave are), you get different kinds of waves. For example, radio waves have a pretty low frequency - that is, the peaks in a radio wave are pretty far apart. Next comes microwaves, then infrared light. Next is the visible spectrum (i.e. the different colors of light that people can see), followed by ultraviolet light. Then waves with  higher frequency are called X-rays and still higher are gamma rays - these have the peaks closest together. 

Sometimes you'll hear that light is made of photons. What that means is that when light is absorbed or emitted, the energy in the wave comes in lumps. The size of those lumps (or "quanta") of energy depends on the frequency. The higher the frequency the more energy per photon.