This document discusses social networks and their impact. It begins by defining social networks as social structures made up of nodes like individuals or organizations connected by relationships. It then provides examples of different types of social networks like Facebook, LinkedIn, and alumni networks. The document outlines key features of social networks like messaging, sharing media, and discusses how they are used for socializing, business opportunities, and matchmaking. It also discusses popular networks like Facebook and Twitter, noting their founding years, user numbers, revenue models, and basic features. The document covers advantages and disadvantages of social networks for individuals and businesses. It concludes that social networks are now a major part of life but have both positive and negative aspects depending on how they are used.