What is significant about the speed of light?

The speed of light is exactly 299,792,458 metres per second, denoted as c – a universal physical constant. This is equivalent to 1 billion kilometres per hour, or 700 million miles per hour. The speed of light in vacuum is the upper limit for the speed at which information, matter, or energy can travel through space. c is not just the speed of light, it is finite, and is considered a universal speed limit for all matter or information. This limit arises directly from the structure of space-time, as described by Einstein’s special relativity. Nothing with mass can travel as fast or faster than the speed of light according to relativity. All forms of electromagnetic radiation, including visible light, travel in vacuum at the speed c as do massless particles and field perturbations, such as gravitational waves.

Source