The document discusses the electromagnetic spectrum, which includes different types of electromagnetic waves that transfer energy, including visible light, infrared, ultraviolet, microwaves, radio waves, X-rays, and gamma rays. These waves have different wavelengths and frequencies and travel through space at the speed of light. Visible light is the only part of the electromagnetic spectrum that humans can see, but all types are forms of radiation. The document provides examples of how different types of electromagnetic waves are used, such as radio waves for communication, microwaves for cooking, and X-rays for medical imaging.