I believe a leader is someone who has the ability to lead / drive a team to reach common goals and visions. A leader is someone who influences others to follow their beliefs and values towards achieving their goals. Anyone can be a leader, but the questions lie whether you are born to be a leader or whether leadership is something that comes through age and life experience. I tend to believe that effective leadership comes from life experiences. Your life experiences shape the way we are, our values and beliefs.
When I think about leaders, I tend to think about my parents as being the first leaders I come across in bringing me up to be an active member in society. Other potential leaders can be teachers, principals, CEO's of companies, politicians, Managers, Supervisors, Directors, etc.