Light travels at a speed of 299,792,458 meters per second in a vacuum.

Here's why it's important to note:

* Vacuum: Light travels fastest in a vacuum, where there's no matter to slow it down. In other mediums like air or water, its speed is slightly lower.

* Meters per second: The standard unit for measuring speed is meters per second (m/s), not kilometers per second (km/s).

Let me know if you have any other questions!