Ok kiddo, do you know what "scandal" means? It's when something really bad happens that people get upset about.
Well, back in the 1970s there was a scandal called "Watergate". It was about some people who worked for the President of the United States, and they did some things that were not good.
One thing they did was breaking into an office building called the Watergate Complex in Washington DC, where some important people worked. They went there to steal some information, but they got caught by the police.
But that's not all! They also tried to cover it up, which means they told lies and tried to hide what they did. Some people in the White House, where the President lived and worked, knew about it and helped to cover it up.
Many reporters and investigators worked hard to find out what really happened, and they found out that the President's advisors were involved. They even found a secret tape that the President had made of conversations with his advisors, which proved that the President knew about what happened at Watergate and had tried to cover it up.
So, the President had to resign (which means he quit) because he was caught in a lie and couldn't be trusted anymore. It was a very important event in American history because it showed that nobody, not even the President, is above the law.