Imagine that you draw a picture and you want everyone to know that it's your picture. You could write your name on it with a pen, but what if someone else comes along and erases your name? That would make you sad. A digital watermark is like writing your name on a picture, but way smarter and more secret.
A digital watermark is a little bitty image that you can't even see, and it's put on top of another image, like a picture or a video. But instead of being a normal image, it's like a special code that only computers can read. This code says, "Hey, I belong to this person or this company!"
The cool thing about a digital watermark is that you can't just take it off like you might be able to erase a name from a picture. Even if someone tries to change the picture around or copy it, the watermark will still be there. So it's like your very own secret stamp that you can put on all your pictures and videos to make sure everyone knows they're yours.