A VPN is built over public infrastructure while WAN is a private network with routers mainly owned by the organization. Computers in a WAN setting communicate via packet or circuit switching, but VPN users must set a connection and tunnel through the public network to the destination.
Choosing between WAN or VPN depends on various factors including reliability, budget, bandwidth and future organizational needs. A WAN network is formed through a collection of numerous LAN networks and data is mostly multiplexed with data from other sources and moved as packets by small computers called packet switchers. WANs are implemented to increase the geographical coverage from the smaller LANs. These networks are usually more expensive in comparison with other remote connectivity methods.
A VPN is typically a form of WAN network equipped with the ability to communicate via public network, such as the Internet, or over a public telephone network, unlike the WAN which is set up over "leased lines." This makes a VPN heavily guarded, with security measures such as solid authentication and encryption techniques. VPNs are implemented to ensure secure movement of data, and the users at both ends view their communication as though through a dedicated private link. These networks tend to be cheaper than traditional WANs.