The document discusses the history and definitions of the Internet, intranet, and extranet. The Internet began in the 1960s as the ARPANET network established by the US defense industry. It later expanded and became publicly available, now offering information access and communication globally. An intranet is a private network that securely shares information within an organization. An extranet allows selective internal information from an organization to be accessed by external partners and remote employees outside the corporate firewall but still maintains some security. The key differences between these networks are their size, accessibility, security features, and intended users.