Social networks comprise a set of nodes or actors (representing, e.g., individuals, groups, organisations) that are pairwise connected by edges or ties (representing, e.g., relationships, interactions, communication). The social systems arising exhibit patterns of interest, and social network analysis is the study of how and why these patterns emerge, sustain, and evolve. Of primary interest is thus to understand and describe the social processes that support the observed structure. These processes are founded in theories about network representation and theories about observed social phenomena. The benefit from network conceptualisation is thus obtained by outlining the association and distinction between these theories. This entry serves as an introduction to fundamental network concepts and analytical approaches, their potential for studying social phenomena, and a description of why they are central to theoretical constructs. This entry also provides a short introduction to statistical network modelling for cross-sectional and longitudinal network data.