Okay kiddo, have you ever heard of a "report card"? It's something you get from school that tells your parents how you're doing in class.
Well, just like a report card, there's something called an "adverse event reporting system," but for grown-ups. It's a way for people who make things like medicine or medical devices to keep track of any bad things that happen to people who use their products.
For example, let's say you take a cough medicine and it makes you feel really sick. You or your parents can report that bad thing (the adverse event) to the people who make the medicine so they can investigate and figure out what happened.
The goal of the adverse event reporting system is to make sure that the things we use to stay healthy are safe and effective for everyone.