Okay kiddo, let me tell you about something called estoppel by deed. Imagine you have a special toy that you want to give to your friend. You promise to give it to them and they get really excited! But then, if for some reason you can't give it to them, they might be really disappointed. Estoppel by deed is like that, but for grown-ups and property.
When someone sells their property to another person, they sign a special paper called a deed that says they are the owner and they are selling it to the new person. The new person gets really excited, just like your friend, and thinks they own the property now. The seller is also making a promise that they are the owner and have a right to sell it.
Now, let's say after some time, it turns out that the seller didn't actually own the property they sold. Maybe there was a mistake or something. Normally, this would be a problem, and the new person might be really upset. But because of estoppel by deed, the seller made a promise on that paper (the deed) that they owned the property, and the new person relied on that promise when they bought it. This means that the seller can't take back their promise and say they didn't actually own the property. The new person is protected by the promise made on the deed, just like your friend was protected by your promise to give them the toy.
So, in short, estoppel by deed means if someone promises on a special paper (the deed) that they own a property and sell it to someone else, they can't later go back on that promise if it turns out they didn't actually own the property. This helps protect the person who bought the property and relied on that promise.