There are many definitions for Leadership but most agree the following defines it well;

Leadership is "organizing a group of people to achieve a common goal." The leader may or may not have any formal authority. 

• listen openly to others
• offer and accept constructive suggestions
• give clear directions
• set and meet deadlines
• give formal and informal presentations
• help members identify and solve problems
• set an example of desired behavior
• show appreciation of others' contributions
• show understanding
• encourage members to exchange ideas
• handle conflict
• guide the group in goal setting and decision making
• delegate responsibilities
• ask questions of the group to prompt responses
• create a productive atmosphere

• They are honest. This gives them credibility, resulting in the trust and confidence of their people. Credible leaders foster greater pride in the organization, a stronger spirit of cooperation
  and teamwork, and more feelings of ownership and personal responsibility.
• They do what they say they will do. They keep their promises
  and follow through on their commitments.
• They make sure their actions are consistent with the wishes
  of the people they lead. They have a clear idea of what others
  value and what they can do.
• They believe in the inherent self worth of others.
• They admit to their mistakes. They realize that attempting to
  hide a mistake is damaging and erodes credibility.
• They create a trusting and open climate.
• They help others to be successful and to feel empowered.
• They don't push too much. They encourage members to do
  more, but know when it's too much.
• They roll up their sleeves. They show the members they aren't
  just the figurehead or decision maker. Members respect
  leaders more when they show the willingness to work alongside
  them.
•  They avoid phrases that cause resentment, reluctance and
  resistance. For instance, instead of saying you have to do something, effective leaders request or recommend that members do something.