This document defines and describes different types of computer networks. It explains that a computer network connects computers together to share resources. There are three main types of networks based on size: local area networks (LANs) which connect computers within a single site or building; metropolitan area networks (MANs) which connect LANs over a larger geographic area like a city; and wide area networks (WANs) which interconnect LANs across geographic distances that could span multiple cities or countries. The key differences between these network types are their size, connection technology, and purpose.