A wide area network (WAN) is a large computer network that connects groups of computers over large distances. WANs are often used by large businesses to connect their office networks; each office typically has its own local area network, or LAN, and these LANs connect via a WAN. These long connections may be formed in several different ways, including leased lines, VPNs, or IP tunnels (see below).
The definition of what constitutes a WAN is fairly broad. Technically, any large network that spreads out over a wide geographic area is a WAN. The Internet itself is considered a WAN.
Source : Cloudflare
