Okay kiddo, let me explain what happened during the financial crisis of 2007-2008 in a way that you can easily understand.
So you know how people save their money in banks, right? These banks take that money and give it to other people who need to borrow it, like when someone wants to buy a house or a car. But sometimes, people borrow more money than they can pay back, which means the bank loses that money.
Well, in the mid-2000s, banks started giving out loans to people who couldn't really afford to pay them back. This was called subprime lending. It was risky, but it could also be very profitable for the banks. As more and more people took out these loans, the banks thought they were making lots of money.
But then, in 2007, the housing market in the United States started to go down. That meant that people who had taken out loans to buy homes suddenly owed more money than their homes were worth. And because they couldn't pay back these loans, the banks started losing lots of money.
At the same time, banks were also investing in some really risky financial products, like mortgage-backed securities. These things were tied to the value of homes, so when the housing market crashed, these investments became worthless.
As the banks lost more and more money, they started to panic. They realized that they didn't have enough money to cover all of the loans and investments they had made. This led to a general loss of confidence in the banking system, as people and other banks became afraid that these banks were going to fail and they wouldn't get their money back.
This all caused a big panic in the financial markets. Stock prices went down, people lost their homes, and businesses that relied on credit (like car manufacturers) started to fail.
So, in a nutshell, the financial crisis of 2007-2008 happened because banks were too eager to make money by giving out risky loans and investing in risky financial products. When those bets went bad, the banks lost a lot of money and caused a lot of problems for the entire economy.