Anyone who emotionally or physically hurts another person is a bully and bullies should be stopped immediately. Bullies seem powerful but they are often weak people who are unhappy with themselves, or they have an upsetting life themselves that leads them to making others feel bad to "big themselves up" or to make themselves feel better.
If you are being bullied the best thing you can do is TELL someone. Tell your friends, tell an adult you trust whether it be a teacher or relative, but TELL someone. The faster other people become aware of the situation, the faster it can be solved. Do not be afraid to tell someone. If the bullying is too bad to ignore, tell someone and get it sorted! Being bullied can make you a stronger person, whereas the bullies will remain weak and sad people.
In the end, there is only one winner: You!