Social institutions are a central object of study within the social sciences, they represent enduring patterns of organization or structures built up around some social function, religions, governments, and families are all institutions that have stood the test of
Within any given social system a number of collective functions need to be performed for the system to be maintained and develop over time, these functions might include, basic biological reproduction of the population, for which we have the institution of the family, or economic functions such as manufacturing products, for which we have businesses or political functions such as collective social decision making for which we have the institution of government.
In the social sciences, social structures are the patterns of social arrangement in society that are both emergent from and determinant of the actions and relations between agents, as enduring patterns of behavior and interaction they define some form of order to the overall system.
A social network is an abstract representation of a social system in terms of its relations and structure of connectivity. The basic constituents of a social graph are nodes and edges, nodes are people or groups of people, edges - also called ties - represent the relationships between these social actors, which can come in many different kinds, such as friendship, kinship, colleague etc.
Social network structure describes the makeup of the overall social network. There are a number of major factors shaping the overall make-up to a social network including the density of connections being a primary factor as it tells us how connected an agent is on average; the average path length is a second key overall metric as it tells us how close together any two agents are on average.