Okay kiddo, so the United States wanted to know what the Soviet Union was doing, without the USSR knowing about it. So they sent airplanes with cameras up in the sky to take pictures of all the buildings and things on the ground.
But they had to be really sneaky about it, so they flew the planes very high up in the air and very fast, so the Soviets couldn't shoot them down or catch them.
The cameras in the planes were really good and could take pictures of things on the ground from really far away. They even had special cameras that could take pictures at night using infrared light, which is like a special kind of light that our eyes can't see.
The pictures that the planes took were very important to the United States because it helped them see what the Soviets were up to and if they were building anything dangerous. But they had to keep it all secret, so not many people knew about it for a long time.