Although there are innumerable complex systems and therefore a large number of networks, the focus of this book is social networks. A social network contains individuals as nodes and links representing the relationship between these individuals. The study of social networks is of particular interest because it focuses on this abstract view of human relationships which gives insight into various kinds of social relationships ranging all the way from bargaining power to psychological health. We descibe in detail graph theory, statistical properties and graph algorithms. Through this, we hope to describe the various patterns and statistical properties of networks, introduce design principles and models for looking at these properties, provide an understanding as to why networks are organized the way they are and apply our understanding to predict behaviour of networks.