Hey there! Have you ever had some cool stickers or toys that you thought were valuable and someone else wanted to give you money for them? Well, money is like those stickers and toys- people think it's valuable and are willing to trade things they have or do for it.
Now, in some places, there might be older stickers or toys that are not used much anymore but people are still holding onto them. These older stickers or toys represent the older money that people used to use in the past. The government may decide that they don't want these older stickers or toys to be used as money anymore because they might not have as much value as newer ones.
So, what the government might do is announce that these older stickers or toys will no longer be accepted when people are trying to buy things in stores or trade for other things. This announcement is called "demonetization in legal tender." It basically means that the older money is no longer legal tender, which is another way of saying that it's no longer considered valuable for trade.
This might cause some people to be upset because they have a lot of the older money and don't know what to do with it. They might have to go to a special place to exchange their old stickers or toys for newer ones or deposit them in a bank account. But ultimately, the goal is to make sure that everyone is using money that is considered valuable and up-to-date.