There are face to face gatherings of people which don't match this definition, such as mobs and gangs. Groups may be formally established and designed, or they may be an informal gathering of individuals. Some groups are formed to address continuing tasks, while others may be ad hoc in nature, disbanding after completing a task. Groups form for many reasons and in many ways. Common concerns or problems among people often lead to the formation of several people into a group.
Proximity is another common reason for group formation.
The necessity of additional expertise in accomplishing a task can also lead to the formation of a group. People enjoy sociable activities and may form groups to derive pleasure for that reason. Groups are a pervasive fact in organizations. Whether formal or informal, organized for a particular task or for continuing communications among members, groups will occupy many hours of your time spent in organizations. Your instructor once attended a management club meeting of a firm at which one of the participants announced publicly that he intended to reduce the time he spent in group meetings from 38 to 25 hours per week.