The eletromagnetic spectrum desribes wavelengths of

The wavelength of light.

The electromagnetic spectrum shows the parts of light orchestrated by their wavelengths. The range for the most part comprises of both visible as well as invisible light. Together, they are called electromagnetic radiation. They are electromagnetic in light of the fact that they comprise of both an electric field and an magnetic field, and these fields travel in wave and travel at the speed of light: 3.00 × m/s.  

When the light gets scattered it gives out color in the form of VIBGYOR which is elaborately called as Violet, Indigo, Blue, Green, Yellow, Orange and red. These colors are arranged in the spectrum based upon the wavelength.