LAN stands for local area network. It covers, as the name suggests, a local area. This usually includes a local office and they’re also pretty common in homes now, thanks to the spread of Wi-Fi.
Whether wired or wireless, nearly all modern LANs are based on Ethernet. That wasn’t the case in the 80s and 90s, where a number of standards, including NetBEUI, IPX and token ring and AppleTalk. Thanks in large part to its open technology, Ethernet rules supreme. It’s been around since the early 70s and isn’t going away anytime soon.
There are two ways to implement Ethernet: twisted-pair cables or wireless. Twisted pair cables plug into switches using RJ-45 connectors, similar to phone jacks. (Remember those?). Cables plug into switches, which can be connected to other networks. A connection to another network is a gateway that goes to another LAN or the Internet.
The other popular Ethernet access method is over Wi-Fi under the IEEE 802.11 standard. Almost all new routers can use the b/g/n standards. IEEE 802.11b and g operate in the 2.4 Ghz spectrum, while n operates in 2.4 and 5 Ghz, allowing for less interference and, thus, better performance. The downsides to wireless are the potential for interference and potential eavesdropping.