Radio is a way of sending sounds through the air using invisible waves called radio waves. When you listen to music or news on a radio, someone at a radio station is converting sounds into these waves, which travel at the speed of light to your radio receiver, where they're turned back into sounds you can hear.

The invention of radio in the late 1800s changed the world. For the first time in history, people could hear voices and music from far away without any wires connecting them. Before radio, if you wanted to hear a concert, you had to be there in person. After radio, a family in Kansas could listen to a baseball game in New York or hear the President speaking from Washington.

Radio waves can travel hundreds or even thousands of miles. They can bounce off the atmosphere and curve around the Earth's surface, which is why you can sometimes pick up stations from distant cities late at night. The same technology that carries music and talk shows also lets police officers communicate, helps ships navigate, and allows air traffic controllers to talk to pilots.

When you radio someone, you're sending them a message using a radio transmitter. A ship in distress might radio for help, or a hiker with a walkie-talkie might radio their friends on the trail.