Imagine you have a friend who wants to build a lemonade stand, but they don't have any money. You want to help out, so you give them a dollar and ask them to pay you back later with some extra money as thanks. This is kind of like a war bond!
During a war, a country needs lots of money to help pay for things like weapons, food, and medicine. The government asks people to lend them money by buying what's called a bond. A bond is like a big IOU from the government, promising to pay the person back with interest after a certain amount of time.
So, let's say the government sells a bond for $50. People like your grandparents might buy one to help support the war effort. They give the government $50 to use, and in return, the government promises to pay them back $75 after a set number of years.
It's important for people to buy war bonds because it helps the government have the money it needs to fight a war. When lots of people buy bonds, the government can use that money to buy supplies for soldiers, help people who have been hurt, and pay for things like airplanes and tanks.
Once the war is over, people who bought war bonds can turn them in and get their money back with interest. So, it's kind of like they made a smart investment while also helping their country during a difficult time!