What Is The Psychological Term For People Who Take Pride In Human Suffering?

Anyone know what the psychological terms are for people who take pride in human suffering or any psychological terms for the following:
People who are bullies.
People who like to torture others.
People who like to get entertainment from harassing others.
People who get their entertainment from watching others get hurt.
People who laugh and get personal joy in the embarrassment or humiliation of others.
I cannot understand why anybody would do any of the above and would like to know why they do. I know there are plenty of people out there who laugh and get personal joy in the embarrassment or humiliation of others. But I just cannot understand why?