Let's back up. The power coming out of your wall is made up of electrons that pulse back and forth in something called an alternating current.
Our devices — laptops, smartphones, tablets, etc. — can't deal with the back-and-forth current. They need a steady stream of electrons to do their thing. So the box on your charger's cord converts the alternating current into something called a direct current.
In the process, energy is lost. That's the heat you feel coming off the box. So why not just send the direct current through our walls? Well, someone else had that idea about a century ago. You may have heard of him: Thomas Edison.
Edison and Nikola Tesla had competing visions for what kind of current, AC or DC, should power America's electric revolution. Edison lost out, but since our new gadgets are all hungry for DC power, his vision could be making a comeback.
To learn more about their rivalry, and how DC power could be making a comeback, check out the video above.
Produced in partnership with NPR's Planet Money. Subscribe to their awesome podcast here.