Explain furlough days in education and how they affect our teachers and students?

I understand that furloguh days are those which teachers are required to not work and are also not given pay. The system is further manipulated by making pre- and post- planning days furlough (in which the teacher really has no option but to work and is refused pay). How much money is this saving the average school district? The state? What are other alternatives rather than taking two days out of each school month?
Do teachers not sign a contract with their salary posted? Furlough days clearly disregard any predetermined salary.
Are superintendents furloughed? Who’s benefitting from this?