The concept of electromagnetic radiation introduces us to the idea that things are not the way we perceive them. This concept applies to more than just e-radiation in life. It is an excellent example of how we should think about other things in life that seem so, so clear. Maybe they really aren't so clear after all.
We see sunlight as white light that allows us to use our eyes during the day and forces us to turn on a floorlamp or flashlight at night. From the gorgeous rainbows left after a storm we know that sunlight can be broken up into different colors.
The makeup of sunlight seems fairly straightforward-logically it would be a wavelength travelling super, duper fast from the sun. If you extend this idea behind what we can see with our eyes, there is an entire spectrum of wavelengths emitted from varying sources (other than just the sun) that serve different purposes. From radio waves (extremely low energy) to cancer-treating gamma rays (extremely high energy) the electromagnetic spectrum has propelled technology in our lives to a level previous thought unattainable.
The seemingly straightforward makeup of white light and other electromagnetic radiation is not so straightforward. The study of this medium led to Einstein's Nobel Prize for the photoelectric effect (light as a wavelength and a particle) and to other phenomena of quantum mechanics. The subatomic processes of light are so different from what we experience in the macroscopic world that it would take an entire degree of classes to really wrap your mind around it.
If you haven't ever goggled the electromagnetic spectrum, I suggest you google it. Do some background reading on a basic science concept that has revolutionized our lives.