To fully understand electromagnetic waves we should familiarise ourselves with the electromagnetic spectrum, (or the EM spectrum), representing all the electromagnetic radiation in the universe. This type of energy is distributed throughout space in the form of electric and magnetic waves. It allows for the transfer of both energy and information.
There are seven electromagnetic groups on the EM Spectrum. On the left of the spectrum exist Radio waves which have the lowest frequency and the longest wavelengths. Planets, stars, and even lightning emit radio waves, and of course, humans use radio waves to communicate sound and information.
Microwaves come next on the EM spectrum, followed by infrared, visible light (the one we can see), Ultraviolet, X-rays, and Gamma rays. What these types of EM radiation have in common is that they all travel at the same speed in the vacuum of space, which is the speed of light. They differ in the fact that each form of EM radiation has a different wavelength and frequency range giving it different qualities.
For example, radio waves are great for communicating information for TV and radio as their long wavelengths allow them to transfer data over long distances within minimal signal degradation.
Microwaves (and radio waves), have long wavelengths and give scientists unique visibility into dense molecular clouds containing nascent stars. These same qualities make microwaves perfect for cooking as their frequencies can penetrate molecules found in food.
Infrared is a great heat source due to its ability to release heat from chemical bonds and it is also used in night vision cameras/goggles.
Visible light of course allows humans to see and do tasks, and UV radiation can help humans produce Vitamin D and is increasingly used to sterilize water.
Gamma radiation has profound medical applications allowing doctors to target and destroy cancer cells.