Okay, kiddo! So, imagine you have a grandma who used to be the queen because she was married to the king, but now the king has died. Your grandma is still important because she was married to the king, but she's not really the queen anymore because the king isn't around.
Now, we call your grandma a "dowager" because that means she was married to the king, but now she isn't the queen anymore because the king is gone. But because she used to be the queen, we call her a "queen dowager" to show that she was married to the king and was once the queen, and now she's still really important even though she isn't the queen anymore.
It's kind of like if you were playing a game and you were the leader, but then someone else became the leader. You're still important because you used to be the leader, but now you're called something else because you're not the leader anymore. That's kind of what a queen dowager is!