Hidden text

When you write something like a secret message in a book but you don't want anyone to see it, you might write it in really small letters, or you might color it the same as the background so nobody can see it. This is called "hidden text". It's like a secret code that only some people can understand, and you have to be very careful when you use it. Some people might use hidden text to cheat or be mean, so it's important to always use it for good reasons.