Okay kiddo, so you know how there are lots of banks out there, right? Well, some banks are really big and important because they do a lot of important work for other companies and people. These banks are called the "Big Four" in banking.
The Big Four are made up of four different banks that are really big and powerful. Their names are JPMorgan Chase, Bank of America, Citigroup, and Wells Fargo. These banks are all based in America, but they have branches and offices all over the world.
The reason these banks are so important is because they have a lot of money and they can do things other banks can't. They can lend money to other big companies, help people buy houses or cars, and they can even invest money in other businesses to help them grow.
Sometimes people are worried that these big banks have too much power and control too much of the financial system. But they are still really important, and they help keep our country's economy strong.
Does that help, little one?