Social Group

In my opinion, 'social group' can be define as two or more humans interact with each other, sharing the same opinion and ideas, and having the same status and lifestyle. A group is defined in terms of those who identify themselves as the members of the group.

From my research and readings, there are too many social group to list down. These are some examples I found from the internet.   

Peer group
A peer group is a group with members of approximately the same age, social status, and interests. Generally, people are relatively equal in terms of power when they interact with peers. 
Clique
A group of people that have many of the same interests & commonly found in a High School/College setting; most of the time they have a name & rules for themselves. 
Club
A club is a group, which usually requires one to apply to become a member. Such clubs may be dedicated to particular activities: sporting clubs, for example. 
Household
All individuals who live in the same home. anglophone culture may include various models of household, including the family, blended families, share housing, and group homes. 
Community
A community is a group of people with a commonality or sometimes a complex net of overlapping commonalities, often–but not always–in proximity with one another with some degree of continuity over time. 
Franchise
An organization which runs several instances of a business in many locations. 
Gang
A gang is usually an urban group that gathers in a particular area. It is a group of people that often hang around each other. They can be like some clubs, but much less formal. They are usually known in many countries to cause social unrest and also have negative influence on the members and may be a target for the law enforcers in case of any social vices 
Mob
A mob is usually a group of people that has taken the law into their own hands. Mobs are usually groups which gather temporarily for a particular reason. 
Posse
A posse was originally found in English common law. It is generally obsolete, and survives only in America, where it is the law enforcement equivalent of summoning the militia for military purposes. However, it can also refer to a street group. 
Squad
This is usually a small group, of around 3 to 15 people, who work as a team to accomplish their goals. 
Dyad
This is a social group with two members. Social interaction in a dyad is typically more intense than in larger groups because neither member shares the other's attention with anyone else. 
Triad
This is a social group with three members, which contains three relationships, each uniting two of the three people. A triad is more stable than a dyad because one member can act as a mediator should the relationship between the other two become strained. 
Team
similar to a squad, though a team may contain many more members. A team works in a similar way to a squad. 
In-group
It is a social group toward which a member feels respect and loyalty. It is a group that an individual identifies in positive direction. If a person is part of the in-group then they are collectively part of an inner circle of friends. An inner circle may contain sub-groups within the inner circle including the apex (best friends), core (very close friends), outer rim, etc. This group provides a support structure and being exclusive offers protection from anyone in an Out-group (see below.) 
Out-group
It is a social group toward which a person feels a sense of competition or opposition.It is a group that an individual identifies in negative direction.

Ref : http://en.wikipedia.org/wiki/Social_group