The LAN stands for Local Area Network. It is a computer network that interconnects devices within a limited geographical area, such as a single laboratory, an office building, a factory floor, or a home. The defining characteristic of a LAN is its local scope, which distinguishes it from a Wide Area Network (WAN) that spans large geographic distances (like the Internet) or a Metropolitan Area Network (MAN). The most common technology used to implement a wired LAN is Ethernet.
An Ethernet LAN allows computers, servers, printers, and other network-enabled devices to communicate with each other and share resources. In the context of modern programmable instruments, a LAN port (using an RJ-45 connector) is a very common interface for remote control. Instruments that are LAN-enabled can be connected to the local network and controlled by any computer on that same network. This offers significant advantages over older point-to-point interfaces like RS-232C or USB. It allows for control over much longer distances (limited only by the network infrastructure) and enables multiple instruments to be controlled from a single PC without complex cabling. It also allows for multiple computers to potentially access a single instrument (though typically not simultaneously for control).
LAN-based control is the foundation for the LXI (LAN eXtensions for Instrumentation) standard, which provides a framework for ensuring interoperability and synchronization of instruments over an Ethernet network.