Social networks are like cities where people can communicate, form relationships, play games, get information, shop, and vote. A social network consists of individuals or organizations (nodes) that are connected through relationships like friendship, family, financial exchange, interests, or prestige. Social media are media created and shared through social interaction rather than traditional publishers or algorithms. This document discusses how individuals and businesses use social networks professionally and personally, and how social networks and cities make money through services like advertising or membership fees.