This document defines and describes computer networks and the two basic types: local area networks (LANs) and wide area networks (WANs). A computer network is a system of two or more connected computers that can communicate and share resources electronically. LANs typically connect computers within a single building or residence to share printers, servers, and other devices, covering distances up to 1 km. WANs connect LANs over larger geographical areas through shared communication paths and provide connectivity between distant locations, with the Internet being a common example. Examples and diagrams are provided to illustrate both LANs and WANs.