A subpage is like a secret room that's connected to a bigger room. Imagine you have a big room with a door, and behind that door is a smaller room. That smaller room is the subpage! It's part of the bigger room, but it's hidden away and you need to know where the door is to find it. On a website, a subpage is a page that's connected to a main page, but you have to click a link or a button to access it. So, if the main page is like the big room and the link or button is the door, the subpage is like the secret room. It's still part of the website, but it's not as easy to find as the main pages.