How does one decide who is and who is not a manager in a given organization?

Generally, if someone assigns work to others, and/or supervises the work of others, and/or is responsible for completing performance reviews to evaluate the work of people who "report to them", then they are a manager. However, some companies give the title Manager to someone who does not meet any of these criteria as a way of putting them into a job title that has a salary range adequately high so as to convince the person to accept the job, even though they are not actually managing/supervising other employees.