Imagine there are many different banks in the world. Some banks are smaller than others and some are bigger. The biggest banks are called "bulge bracket" banks.
These banks deal with very big and important clients, such as large corporations or governments, and they offer a wide variety of services like managing investments, providing loans and helping with acquisitions or mergers.
Think of it like playing a game of basketball. The big banks are like the tallest and strongest players on the court, because they have a lot of money and expertise to offer. They are the ones who get to take the most important shots and make the biggest plays.
Overall, the term "bulge bracket" is used to group together the biggest and most prestigious banks around the world, although there is no official definition for it.