LAN - Local Area Network
A LAN is the standard kind of network that you will see in a digital home or office. It consists of one small local sub network, and may have a local router/gateway connecting it to a broader network or the internet.
With WiFi technology, it is possible to use LAN systems for building robots - indeed a few microcontroller boards now ship with either a WiFi system or a wired ethernet port for LAN communications. This means you can build communication systems between robots and computers on well known internet protocols.