Okay kiddo, so sometimes when we talk, we don't say exactly what we mean to say. That mistake we make is called a "slip." For example, if you meant to say "I want to eat pizza" but instead said "I want to eat piza," that's a slip.
Now, there's a guy named Freud who studied why people do things they don't mean to do. He came up with this idea called the "Freudian slip." That means when we make a slip, it can tell us something about what we're thinking or feeling inside.
Let's say you're really mad at your friend, but you don't want to tell them that. If you accidentally call them by the wrong name, like "Sara" instead of "Sarah," that could be a Freudian slip. It might mean that deep down, you're still really angry at them.
So, a Freudian slip is when we say something by accident that reveals our true thoughts or feelings. It's like a little secret that slips out without us even meaning to say it!