difference between a diary or online
When you write in a diary it is more private because nobody can see it unless you let them see it. If you write something mean about someone they cant see it unless you let them see it.
When you write online its not as private. Anyone can see it. When you write something mean about your friends they can see it and they might get mad at you. If you are going to college or applying for a job, they may look at what you post online.