The term Wide area network (WAN) is used to describe a network that is spread over multiple geographic locations. Let’s take an example. A company has two offices, one in London and one in Berlin. Both offices have a LAN. When a company connects these two LANs together using a WAN technology , it creates a Wide area network (WAN).
The key difference between LANs and WANs is that the company usually doesn’t own WAN infrastructure. A company usually leases WAN services from a service provider. A WAN spanning multiple cities could look something like this:
Frame Relay, ATM and X.25 are different types of WAN technologies. We can also consider the Internet to be a WAN.