Okay kiddo, so do you know what online shopping is? It's when you buy things on the internet and they get delivered to your house. Now, some companies only have stores in certain states, but they can still sell things online to people in other states.
But there's a law called "sales tax" that some states make companies pay when they sell things to people who live there. It's like a little extra tax that helps pay for things like schools and roads.
Some companies, like Wayfair, didn't think they had to pay sales tax in certain states if they didn't have a physical store there. But South Dakota wanted them to pay the tax anyway, even if they didn't have a store in the state.
So, Wayfair and South Dakota went to court to see if Wayfair had to pay the tax, even if they didn't have a store in the state. And the court said yes, that Wayfair had to pay the tax.
It was a big deal, because it made it harder for companies to avoid paying sales tax in states where they didn't have stores. And it meant that states could get a little more money to help pay for things that they need, even if people were shopping online.