A number of individuals, defined by formal and informal criteria of membership, who share a feeling of unity or are bound together in relatively stable pattern of interaction are called social groups. Sociology is primarily concerned with social relations and how these relations develop as a result of social interaction. When some people establish social relations with one another, their gathering is called a group. Direct or indirect relations between two or more people is the fundamental basis of a social group. A collection of human beings may be called a group only when it has a permanent set of patterns. The members need to influence one another by their internal activities. When members establish relationships on the basis of common characteristics and goals and influence each other, it is called a group Social groups differ in size, ranging from intimate associations, like a family to large collectivities such as a political party. Groups are organised system of two or more individuals. People join groups because they provide security, status, self-esteem, satisfaction of one's psychological and social needs, goal achievement, knowledge and information. Group formation is a natural process of society. Proximity, similarity and common motives and goals facilitate group formation. Groups are of different types i.e. primary and secondary, formal and informal and 'in-group' and 'out-group'. Primary groups are preexisting formations in which face to face interaction is possible and relationship bonds are based on personal relationship. In primary groups a person knows one another well and they establish close relationship among them, boundaries are more permeable. Secondary groups are those where relationship among members are more impersonal, indirect and less frequent. In this group it is easy to leave and join another group. Secondary groups provide experience lacking in intimacy. Formal groups differ in degree to which the functions of the group are stated explicitly and formally. The functions of a formal group are explicitly stated as in the case of an office organisation. The roles to be performed by group members are stated in the explicit manner. The formal and informal groups differ on the basis of structure. The formations of formal groups is based on same specific rules or laws and members have definite roles.There are a set of norms which help in establishing order:
On the other hand, the formation of informal groups is not based on rules or laws and there is close relationship among members. Formal groups are groups that are arranged and organised e.g. university. Formal groups tend to be large or a part of large organisation having a normative hierarchial structure. Informal groups are typically small and casually or spontaneously formed and function without formal rules, goals or leaders. The term in-group refers to one's own group, and out-group refers to another group. For in-group members, we use the word 'we' group while for out-group members the word 'they' group is used. By using the word 'they' and 'we', one is categorising people on similar or different basis. It has been found that persons in the in-group are generally supposed to be similar, are viewed favourably, and have desirable traits. Members of the out-group are viewed differently and are often perceived negatively in comparison to the in-group members. Perceptions of in-group and out-group affect our social lives. Co-operation and proximity are common features of in-group members. Hostile and aggressive relationship leading to conflict and competition is common feature towards out-group members. In-group members maintain mutual dependence, solidarity, faithfulness, friendship, cooperation and communication for members whereas out-groups are known as stranger group.