In quite a few theories, social relations are considered channels that transport information, services, or goods between people or organizations. In this perspective, social structure helps to explain how information, goods, or even attitudes and behavior diffuse within a social system. Network analysis reveals social structure and helps to trace the routes that goods and information may follow. Some social structures permit rapid diffusion of information, whereas others contain sections that are difficult to reach.

This is a bird’s-eye view of an entire social network. However, we can also focus on the position of specific people or organizations within the network. In general, being well connected is advantageous. Contacts are necessary to have access to information and help. The number and intensity of a person’s ties are called his or her sociability or social capital, which is known to correlate positively to age and education in Western societies. Some people occupy central or strategic positions within the system of channels and are crucial for the transmission process. Such positions may put pressure on their occupants, but they may also yield power and profit.

In this part of the book, we focus on social networks as structures that allow for the exchange of information. In this approach, the direction of ties is not very important, so we discuss only undirected networks (with one exception). In Chapter 6, we present the concepts of centrality and centralization. In Chapter 7, we discuss the structure of the immediate network of actors, especially the pressure or power that is connected to particular structures of this ego network. In Chapter 8, we take time into account as we study the role of network structure in the diffusion of innovations and diseases.