Imagine there are a lot of different kinds of people in the US and sometimes people make assumptions about them because of what they look like or where they come from. These assumptions are called stereotypes. For example, some people might think that all people who come from Mexico are lazy or all people who have brown skin are criminals.
But just because someone looks a certain way or comes from a certain place doesn't mean that they are all the same. Everyone is different and unique, and we shouldn't judge people based on stereotypes. It's important to get to know people as individuals and not make assumptions about them based on what we think we know.