Market value is the amount of money that something is worth if you were to sell it today. Let's say you have a toy car that you want to sell. If many people are interested in buying it, and you have a lot of offers for it, then the market value of the toy car will be high. However, if no one is interested in buying it, then the market value will be low.
Market value can also be applied to things like stocks and houses. Stocks are little bits of ownership in companies that are publicly traded and bought and sold on the stock market. The market value of a stock is the current price that people are willing to buy and sell it for. Similarly, the market value of a house is what people would be willing to pay for it in the current real estate market.
Overall, market value is simply the worth of something based on supply and demand. It can change quickly depending on many different factors, such as how many people want to buy it, how popular it is, or what other people are willing to pay for it.