LANs: Small area like an office or school. Can be through ethernet, or through WiFi (WLAN).
MANs: Metropolitan Area Network, spans the size of a city or a large university campus.
WANs: Wireless Area Networks. Interconnection across large distances, like cities or countries. Usually use fibre-optic.
SONET/SDH: Synchronous Optical Networking (SONET) and the international equivalent Synchronous Digital Hierarchy (SDH) carry data over large distances through