The electromagnetic spectrum is the scientific name for all of the types of known radiation in the universe.
From shortest (highest frequency) to longest (lowest frequency) wavelengths, they are:
Gamma rays, X rays, ultraviolet rays, visible light rays, infrared rays, and radio waves, which include microwaves, television and FM radio waves, shortwaves, and AM radio waves.
Electromagnetic radiation is everywhere and surround us every second, but visible light is the only radiation we can see.
The electromagnetic spectrum of an object is the unique distribution of electromagnetic radiation emitted or absorbed by the particular object.