Many people used the words team and group interchangeably, but there are actually a number of differences between a team and a group in real world applications. A number of leadership courses designed for the corporate world stress the importance of team building, not group building, for instance. A team's strength depends on the commonality of purpose and interconnectivity between individual members, whereas a group's strength may come from sheer volume or willingness to carry out a single leader's commands.
It is often much easier to form a group than a team. If you had a room filled with professional accountants, for example, they could be grouped according to gender, experience, fields of expertise, age, or other common factors. Forming a group based on a certain commonality is not particularly difficult, although the effectiveness of the groups may be variable. A group's interpersonal dynamics can range from complete compatibility to complete intolerance, which could make consensus building very difficult for a leader.
A team, on the other hand, can be much more difficult to form. Members of a team may be selected for their complementary skills, not a single commonality. A business team may consist of an accountant, a salesman, a company executive and a secretary, for example. Each member of the team has a purpose and a function within that team, so the overall success depends on a functional interpersonal dynamic. There is usually not as much room for conflict when working as a team.
The success of a group is often measured by its final results, not necessarily the process used to arrive at those results. A group may use equal parts discussion, argumentation and peer pressure to guide individual members towards a consensus. A trial jury would be a good example of a group in action, not a team. The foreperson plays the leadership role, attempting to turn 11 other opinions into one unanimous decision. Since the jury members usually don't know one another personally, there is rarely an effort to build a team dynamic. The decision process for a verdict is the result of group cooperation.
A team, by comparison, does not rely on "groupthink" to arrive at its conclusions. An accident investigation team would be a good example of a real world team dynamic. Each member of the team is assigned to evaluate one aspect of the accident. The team's expert on crash scene reconstruction does not have to consult with the team's expert on forensic evidence, for example. The members of a team use their individual abilities to arrive at a cohesive result. There may be a team member working as a facilitator for the process, but not necessarily a specific leader.
Group building can literally take only a few minutes, but team building can take years. Individual members of a group often have the ability to walk away from the group when their services or input become unnecessary. A team member's absence can seriously hamper the abilities of other team members to perform effectively, so it is not uncommon for individual members to form an exceptionally strong allegiance to the team as a whole. An elite military unit such as the US Navy SEALS or the Army Rangers could be considered examples of team building at its best.