"Management" means the people who have authority in a company or a department: managers, directors, vice presidents, etc.
People talk about "Management" when they want to make a distinction between normal employees in a company and the people who make important decisions. Even someone who is a boss or manager can use the word "Management" to talk about the people who rank higher in the company:
Sorry, I don't like this policy either but it's coming straight down from management. There's nothing I can do about it.