What is actually creating the light in the light bulb?

The light in the light bulb is simply the resultant of photon emission through a thin filament often made of tungsten.

Explanation :

Explaining the structure, a light bulb is simply composed of a metal base with two metal contacts. These contacts are attached to the current conducting wires that are attached to a thin filament often made of Tungsten.  

The whole system is enclosed within a light bulb filled with an inert gas Argon. On connecting the light bulb to the electric supply, the current flows through the wires and heats up the filament that emits photons, containing visible light energy. This is how we get a lighted bulb.

The invention of a light bulb has always been one of the biggest inventions in the world of science and technology that has lightened up not only the world but the lives. All credit goes to Sir Thomas Alva Edison and Sir Joseph Swan.