To be an effective people we need to work together towards a common goal in a coordinated and cooperative manner. Therefore you could say that team building is a systematic process designed to improve working relationships and team functioning such as problem solving, decision making and conflict resolution that enables the group to overcome any goal blocking barrier.
For many organizations this result orientated mission is the real purpose for team building. A teambuilding corporate training goals is to identify and develop effective communication.
Another way of looking at it is that team building is like coaching but for a collective group.
“Coming together is a beginning; keeping together is progress; working together is success.” JD Rockefeller