Light waves, a form of electromagnetic radiation, are energy-carrying waves able to self-propagate through the vacuum of space at 3x10^8 meters per second. While "light" sometimes colloquially refers to the entire electromagnetic spectrum, visible light is actually a very small part of it.
Electromagnetic radiation is created any time charged particles, such as electrons or protons, are accelerated, creating an oscillating electric field, which in turn creates a perpendicular magnetic field. Electromagnetic waves are the synchronized oscillations of these electric and magnetic fields propagating in a vacuum at the speed of light. Different wavelengths are the result of various amounts of energy and momentum. These differences manifest themselves in various ways; visible light and the various colors of it, X-rays, nuclear radiation such as gamma rays, and radio waves are some examples.
Electromagnetic radiation differentiates itself by its ability to propagate through a vacuum, while other forms of energy, such as sound waves and shock waves, require a physical medium to interact with and move through. Electromagnetic waves are necessary for life on Earth and also have come to find a special place in science. Knowing and understanding the speed at which electromagnetic waves propagate, 3x10^8 meters per second, or the speed of light, is instrumental in many equations that make everyday life as well as major scientific discoveries possible.