Managing an organisation is about planning, organising, directing, controlling and monitoring the myriad aspects of a company in order to get things done and to reach a clear, defined set of objectives.
Leadership is about creating lasting, purposeful change.
Leadership is not a quality. Nor is it a role. Nor an attribute that some people are lucky enough to be born with. It is a behaviour, an activity, a way of doing things.
Leadership is also a culture. Many people can share the role of leadership in an organisation. The more people, the more effective leadership becomes. One person may be accountable for leadership but in the best companies everyone shares the responsibility.