The individual contributor role
A single employee cannot be a small group of loosely-connected individuals with no formal reporting structure. This is how a team of four people will look like when an individual contributor works for a manager:
In order to create effective teams, a manager must hire two people who fit the “individual contributor” role.
The individual contributor is a person with super-human focus (a typical champion programmer), an exceptionally good idea of how to do things right and an inexhaustible enthusiasm towards what they do. The best of them will usually have deep knowledge in one or two technical fields. They are uninterested in other people’s business, but will readily help fellow team members whenever asked for advice. They will not be able to give detailed instructions about how the tasks are to be completed, but know what’s needed — and how things need to be done.

The manager role
When an individual contributor works for a manager, the manager is more than just a coordinator; she also needs to be a leader. She helps her team accomplish specific goals by setting priorities, providing support and coaching, and making appropriate resource decisions. This means that she has additional responsibilities compared to simply managing her people. This is how the team of four people when an individual contributor works for their manager will look like:
The individual contributor does not report to anyone else but the manager who, in turn, reports to the team’s senior executive.
Managers need to be good coaches and mentors because people learn most from their day-to-day work experiences.
Individual contributors may have been promoted into management positions because of their technical expertise or domain knowledge. Their technical expertise is still important, but if they are to be effective technical leaders, they must learn how to lead a team of people and make decisions.
Leadership is required in the following situations:

How the two roles are different
The key difference between being an individual contributor and a manager is accountability: Individual contributors are accountable for their deliverables and have no authority to make decisions about other people’s work. Managers, on the other hand, are accountable for their team’s results and have the authority to dictate how the team will accomplish its objectives. Individual contributors may be assigned to work on several projects; a project manager stays with a single project from beginning to end.