Describe what the speed of light is and what it means

All electromagnetic radiation (including visible light) moves with a constant speed in a vacuum, commonly known as "speed of light". This is a physical constant that is symbolized with the letter c. It is a universal constant with the value 299 792 458 m / s.

The speed c of the electromagnetic radiation, does not depend on the speed of the object emitting such radiation. For example, the light emitted by a light source that moves quickly, would travel as quickly as the light coming from a stationary source. Therefore the speed of light is constant, and it is the speed at which light waves propagate through materials.