Okay kiddo, have you ever played pretend with your friends? Well, imagine that a bunch of grown-ups got together to do the same thing, but they pretended to plan for a really bad thing happening. This is called a simulation.
Event 201 was one of these simulations where grown-ups from all over the world pretended that there was a really bad virus outbreak happening. They wanted to practice how they would solve the problems that would come with it. They talked about things like how to help sick people, how to get enough medicine, and how to communicate with everyone so that they know what's happening.
Event 201 happened a few months before a real virus outbreak happened in the world called COVID-19. Some people think that the grown-ups who played pretend during event 201 were really smart because they talked about problems that became real later. But others think that it was just a coincidence.