Okay kiddo, so you know how when you want to buy something, you usually have to pay some money for it, right? Well, in economics, when people buy and sell things, we call that a "market." It's kind of like a big playground where people can trade things they have for things they want.
In a market, there are usually lots of people selling the same thing, and lots of people buying the same thing. For example, let's say you want to buy a toy car. There might be a bunch of different stores that sell toy cars, and they all want to sell as many toy cars as possible. But at the same time, there are lots of other kids who also want to buy toy cars, so they can play with them and have fun.
Now, the interesting thing is that the people who are selling the toy cars want to make as much money as possible, while the people who are buying the toy cars want to pay as little money as possible. This is where the idea of "supply and demand" comes in.
Supply is basically how many toy cars are available for sale. If there are a lot of toy cars, then the sellers might have to lower their prices in order to sell them all. But if there aren't very many toy cars available, then the sellers might be able to charge more, because the buyers really want them and are willing to pay more.
Demand is basically how much people want to buy the toy cars. If lots of kids want toy cars and there aren't very many available for sale, then the sellers can charge more money, because they know the buyers really want them. But if not many people want toy cars, then the sellers might have to lower their prices in order to sell them.
So in a market, the prices of things are constantly changing based on how much people want them and how many are available for sale. It's like a big game where everyone is trying to get the most money for what they're selling, while also trying to pay the least amount of money for what they're buying.