What is a set of interconnected local area networks (LANs) commonly known as?

The term used for a set of interconnected local area networks is known as a Wide Area Network (WAN). A WAN typically covers a larger geographic area than a LAN and is designed to connect multiple LANs, enabling communication over broader distances—sometimes globally.

The primary purpose of a WAN is to facilitate communication and data transfer between different LANs, which may be situated in different locations, cities, or even countries. This interconnection is essential for organizations that have multiple offices or branches, as it allows them to share resources, data, and applications effectively.

While LANs are confined to smaller areas like a single building or campus, and other types of networks like Metropolitan Area Networks (MANs) cover larger, more urbanized geographic areas, the WAN acts as the backbone that connects these various networks, making it possible for them to operate together despite being physically separated.