Meta-knowledge is just a fancy word for knowledge about knowledge. It means knowing how we know things or how other people know things.
For example, let's say you read a book about space. You learned a lot of information about planets, stars, and galaxies. That's knowledge! But meta-knowledge would be understanding how you learned that information. You might think, "I learned all of this from reading a book about space."
Another example can be about how we learn. When we learn something new, we usually have to make connections with what we already know. Meta-knowledge would involve knowing that we do this and how it works. We know that the more connections we make, the easier it is to remember and understand new information.
In other words, meta-knowledge is knowledge about how we acquire, process, and organize information. By understanding how we learn and remember, we can become better learners and retain information for longer periods.