Here are some definitions of Leadership from Dictionary.com
the position or function of a leader, a person who guides or directs a group
ability to lead
an act or instance of leading; guidance; direction
the leaders of a group
Below is some information about leadership, that I found at http://www.nwlink.com/~donclark/leader/leadcon.html
You must have an honest understanding of who you are, what you know, and what you can do. Also, note that it is the followers, not the leader or someone else who determines if the leader is successful. If they do not trust or lack confidence in their leader, then they will be uninspired. To be successful you have to convince your followers, not yourself or your superiors, that you are worthy of being followed.
Different people require different styles of leadership. For example, a new hire requires more supervision than an experienced employee. A person who lacks motivation requires a different approach than one with a high degree of motivation. You must know your people! The fundamental starting point is having a good understanding of human nature, such as needs, emotions, and motivation. You must come to know your employees’ be, know, and do attributes.
Below this you can find information about how to be a leader but not come across as being mean or bossy.
When you are a leader, you set a trend, be a role model, set the example, or do the right thing. However, you do not tell someone what they can or cannot do. Some times, you may not know it, but some times you may offend somebody when you are just trying to help them. For example, if somebody didn’t do their homework, and you came up to them, and started saying how they should always do their homework and that they should put first things first when it comes to homework. This, might make it seem like you were trying to tell them what to do when you were just trying to help them in the future. Instead of doing this, you could approach them nicely, and ask them if they need help finding away to do their homework and still do what ever else they have to do.