Electromagnetic radiation is simply a light wave. There are different types of electromagnetic radiation ( to see the electromagnetic spectrum, see below):
Radio waves: Radio waves are the longest waves, and have the lowest energy. Antennae of a television set receive these waves and display them on your T.V.
Microwaves: While it may sound like your home appliance, microwaves are actually long waves that have more energy that radio waves. And yes, microwaves are the waves used to heat your food! However, they are also used for transmitting information because they are excellent at penetrating substances such as rain and snow.
Infrared: Heat comes in the form of far infrared waves, such as the heat we feel from the Sun or a fire. Shorter infrared waves are not hot and can be used in wireless technology.
Visible light: These wavelengths are detectable by the human eye. Each colour has a different wavelength, which our brain interprets and classifies as one of the colours of the rainbow.
Ultraviolet: Ultraviolet, or UV light, has shorter wavelengths than visible light, which renders them invisible to the human eye. Some insects, however, can see them. Sunlight emits UV rays, as do black lights. UV rays have several health effects, both beneficial and harmful. For further information concerning UV health effects, see here.
X-Rays: X-rays have small wavelengths and higher energy levels than UV waves. The use you have most likely heard of is in hospitals. X-rays are shot through your body, but because bones and teeth are more dense than flesh, the X-rays cannot get through, giving an image of your bones.
Gamma rays: Gamma rays have the smallest wavelength and the highest energy level of any wave in the entire electromagnetic spectrum. Gamma rays can kill living cells, which gives them many uses–some positive and some negative.