I can understand how these terms might be synonymous. In an ideal situation, a good manager will be a good leader. Natural leaders will be promoted more quickly to management positions. Of course, this is the ideal that can be written on paper but doesn't always work out in practice. As post 2 suggests, managers aren't always good leaders. Leaders aren't always put in management positions. In order to discuss this topic in a paper or presentation, it might be helpful to define whether you are looking at a real world environment or an ideal business model.