The famous Covey/Benis description is that "managers do things right, leaders do the right things." While useful, I would simply add that leaders create opportunity while managers can improve existing opportunities. Leadership is an Art and Management is Technique. A leader is a person whose actions create a positive influence with positive outcomes. A manager gets things done and makes things better.

It is critical to understand the difference between Leadership and Management.
Management is about (quality, design, charts, lists, deadlines, human resouces, education, performance evaluations, meeetings, ethics, directions, processes, six sigma, change, innovation, entrepeneurship, MBA's, finance, options, all business functions, customer service, human relations, government relations, industry standards, performance measurements, profits, execution etc. Management is everything done to make improvements)
Leadership is that critical moment where courage meets opportunity. The courage to speak truth, the courage to assume responsibility, the courage to trust people. Leadership opportunities arrive every moment and you know them when you see them. Leadership is doing what is right not what is expected. Examples: A parent who hugs their kid when they tell them they just spilt milk on the floor again(concern not criticism), a employer who helps an employee whose car won't start and misses work(maybe we need to pay them more or do we owe them mileage), a manufacturer whose product has failed and their first concern is the welfare of their clients not their bottom line (maybe we need to revisit our design process), a bank who wants customers better off so finds a way to help their institution reach out to potential customers instead of the payday lenders who prey on them(maybe we can make money helping people and not rationalizing that they are better off with payday lenders prices). Leadership is everything.
There is an old saying that life on earth is what we make of it; it can be a heaven or a hell. Leadership is making it heaven for everyone.
Every managerial moment has a leadership opportunity. You can lead to manage but can't manage to lead.(I may have heard that somewhere)