Okay kiddo, so there was a company called Silverthorne Lumber Co. And they were doing some things that the government didn't like. So the government sent some people to Silverthorne's company to take some papers and records that would help them prove their case against Silverthorne.
But Silverthorne didn't like that! And they said that the government wasn't allowed to take their papers without permission. So they went to court to tell the judge that the government was being very mean and did something called an "unreasonable search and seizure".
The judge agreed with Silverthorne and said that the government wasn't allowed to take the papers without permission. But then the government did something sneaky. They used the information they got from looking at the papers they took to make copies of them!
So Silverthorne went back to court again, and they told the judge that the government wasn't allowed to do that! And the judge agreed, saying that the copies the government made were not allowed to be used as evidence against Silverthorne.
So, in short, the case was a big argument about whether or not the government can take stuff from people without permission and then use that stuff against them in court. And the judge decided that the government can't do that, even if they make copies of the things they took.