Okay, so imagine you drew a really cool picture with your crayons on a piece of paper. You're so proud of it, right? But then someone else comes along and scribbles all over your picture or tears it up. That would make you really upset, wouldn't it?
Well, that's kind of like what happens with art vandalism. Sometimes people will take a really pretty statue or painting that someone worked really hard on and they'll spray paint ugly words or pictures on it or they'll break it on purpose. This kind of thing is called art vandalism and it's not nice at all.
The people who make art put a lot of time and energy into creating something beautiful for all of us to enjoy. Imagine if someone destroyed something that you worked really hard on - it would make you feel really sad and angry, right? That's why it's important to respect other people's art and not vandalize it.