Okay kiddo, so you know how in the United States, adults get to vote and choose their leaders? Well, during the 2016 elections, people from a country called Russia tried to mess with that process.
They used fake social media accounts, pretended to be Americans online, and spread all kinds of untrue things about the candidates running for president. They even hacked into emails and released them to the public to make one candidate look bad.
Now, this is not allowed and very bad because it's important that Americans get to choose their leaders without any unfair outside influences. That's why there have been investigations to figure out exactly what happened and how to prevent it from happening again in future elections.