Electromagnetic (EM) radiation is a form of energy that is emitted from energetically excited chemical species. Quantum mechanics tells us that it exhibits both wave-like properties and particle-like properties at the same time. The wave properties have both electric and magnetic components that are perpendicular to each other. You can imagine two waves that are in phase with one another travelling through space with one wave on the x (or horizontal) axis and the other wave on the y (or vertical) axis. The particle properties are quantized (meaning they are in discrete units) with the base unit called a photon. The energy associated with electromagnetic radiation travels through a vacuum at the speed of light and interacts with other objects and chemicals that it comes into contact with, often times imparting its energy to the other objects in both beneficial and detrimental ways.