I would definitely say that I am a team player and a team leader. I take on the responsibility of knowing every job that is done on my tea. I never say "that's not my job," and I expect my teammates to do the same. As a manager, everything falls in your hands if an employee is out. I can honestly say I'm the last to leave and can always be reached when I'm away from the office in the event that my team needs me.
I group is just a bunch of people put together for no apparent reason. A team has a goal and everyone knows their role in helping to achieve that goal.
Teams are so important because no one person can do it all. We all have our strengths. On a diverse team, talents are mixed; where one person is weak, another is strong. Coming together contributing and learning makes everyone involved successful.