A social group is two or more humans who interact with one another, share similar characteristics, and collectively have a sense of unity.
A primary group is typically a small social group whose members share close, personal, enduring relationships.
Secondary groups are large groups whose relationships are impersonal and goal oriented; their relationships are temporary.
In-groups are social groups to which an individual feels he or she belongs, while an individual doesn't identify with the out-group.
Sociologists call any group that individuals use as a standard for evaluating themselves and their own behavior a reference group.
A social network is a social structure between actors, connecting them through various social familiarities.
On the Internet, social interactions can occur in online communities that preclude the need to be face-to-face.