A manager will normally have a team of individuals working with him. His responsibility would be to ensure that the task is completeted in the given span of time by optimally utilizing the skill sets of his team members. His job will include a lot of planning, co-ordinating, organizing, reporting and motivating.
A manager will also have to play the role of a fire-fighter whenever a crisis situation occurs. He will need to do all this and at the same time not lose focus on the task at hand. There is an old saying - "Management is a myth" because only mismangement is visible.