The Internet is the world's largest WAN, or wide area network. A WAN spans a large geographic area, usually by connecting local area networks, or LANS. Most WANS are composed of distributed or collective management and ownership, and are not controlled by any one entity.
Entitles such as VPN-based extranets or the ATM network are also WANS. WANS connect corporate entitles, research networks, government and educational systems. The networks that support private WANS use leased lines and larger, more expensive equipment than LANS. The geographical area of a WAN doesn't have to span continents. In large cities, several major LANS often connect together to form a city-wide WAN.