Every day energy from the sun travels to Earth in the form of electromagnetic radiation, kind of like radio waves but on a different frequency. After it passes through the Earth’s atmosphere, where some of that radiation is absorbed, on a clear day there is typically 1000 W/m2 available on our surface. That may sound confusing because it seems like an immeasurable thing, but usually the amount of available solar power is expressed in units of energy per time per area unit, so how much solar energy is available to be converted into electricity on a meter of surface every minute, hour, etc. This amount obviously will differ depending on where on Earth you are. For example, you’re definitely not going to get as much power at the South Pole as you would near the equator, and not all of the solar energy that hits our surface can be converted to electricity.