Team Building is an active process by which a group of individuals with a common purpose are focused and aligned to achieve a specific task or set of outcomes. 

Team Building simply accelerates the natural process of team formation by setting very clear goals right from the start. A "team building" workshop uses a variety of tools and techniques to accelerate the process further, bringing the team together quickly and effectively. 

Every member of a team is an individual with their own skills, needs and ideas. Being a member of a team does not take away that individual identity, so it is very important to recognise and exploit it. 

Effective team building recognises that individual identity. Effective team building takes individual, personal goals and combines them into a common purpose. Everyone in the team is motivated and driven by what they get out of it, personally. It's easy to all agree to common goals at a team meeting, but when it comes to taking action and making that action consistent, it's very difficult to keep on track if team goals conflict with personal goals. 

A team, by itself, does not exist. We may look at a group of people, working together with common goals and a desire to achieve and call what we see "Teamwork". Really powerful teamwork happens when individuals are working both for their own and for shared goals. They have a sense of commitment and of personal benefit which is powerful and irresistible. 

So, team building is simply a way of actively managing the natural process of team formation by harnessing motivation and setting clearly defined goals and targets.