What are "norms" ? why is it so important for organizations or group to have a set of "norms" by which they function?

"Norms" are informal guidelines about what is considered normal 
social behavior in a particular group. I think it is important that in a certain group there are "norms" because that is just how it is going to work. But, the fashion "norms" that others see, they hate it and change it. The people who are breaking the fashion "norms" i love them for it because we are changing everything and its awesome.