Compare the size of the visible light spectrum with the size of the electromagnetic spectrum.
The range of the visible light spectrum represents a very small segment of the entire electromagnetic spectrum. Visible light ranges in wavelength from approximately 400 nanometers for violet to 700 nanometers for red, which is a range of 4x10^-7 to 7x10^-7 meters. The entire electromagnetic spectrum ranges from 10^-12 meters, smaller than an atom, to 10^2 meters, the length of a football field. Visible light therefore makes up on the order of 1/100,000,000,000,000 of the electromagnetic spectrum. The attached image shows this visually, along with a comparison of frequencies and energies of various types of electromagnetic radiation.
Visible light, in order of long to short wavelength and low to high energy, has the colors red, orange, yellow, green, blue, indigo, violet. An acronym for remembering this is the man's name ROY G. BIV.
All of the forms of electromagnetic radiation from low to high energy (long to short wavelength) are radio waves, radar, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays.