Local Area Network (LAN)
Local Area Network (LAN) is a computer network, which is limited to a small office, single building, multiple buildings inside a campus etc. Typically a Local Area Network (LAN) is a private network owned and maintained by a single organization.
Below image shows a small Local Area Network (LAN) connected together using a Network Switch.
Wide Area Network (WAN)
A Wide Area Network (WAN) spans over multiple geographic locations, which is composed of multiple LANs. It is nearly impossible for a small to medium organization (except Network Service Providers) to pull network cables between their two offices in two different countries located 1000s of kilometers away. Network Service Providers (also called as ISPs) provide the connectivity solutions for Wide Area Networks (WAN).