A LAN is a Local Area Network—a collection of networked devices, including at least one computer, that are wired so as to be able to communicate with each other. A WAN is a Wide Area Network, a system similar to a LAN, but on a larger scale, perhaps encompassing a multi-building facility or a campus. WLAN — not to be confused with WAN — is a Wireless Local Area Network, often called a wireless LAN. This is a LAN with at least one connection that is wireless, rather than wired. A WLAN system is a method of creating a WLAN, and there are several to choose from.
One of the types of WLAN system is the ad hoc mode, or Independent Basic Service Set (BSS), system. Both names indicate that this type of LAN is not in communication with any kind of Access Point (AP), base stations that have a connection out of the local network to the Internet. Another name for this type of WLAN system is peer-to-peer mode. It can be created using equipment with WLAN PC cards or with WLAN dongles.
A WLAN system can also include an AP, either as an independent device or in a router. Any AP and its connected devices are called a Basic Service Set (BSS), which clarifies the acronym IBSS used for an ad hoc WLAN system. If two or more Basic Service Sets are in the same subnet — a physical or logical division of a WLAN — then an Extended Service Set (ESS) has been created. Regardless of whether one is dealing with a BSS or an ESS, this type of WLAN system is called infrastructure mode. Therefore, in choosing the best WLAN system, you need to decide whether you need a BSS, an ESS, or an IBSS.
Another important consideration is the version or versions of the 802.11 standard — the WiFi standard set by the Institute of Electrical and Electronics Engineers (IEEE) — to use. The most common choices are 802.11b, 802.11g, and 802.11n. The choice depends on the standards of the equipment being used to construct the WLAN system, and a consideration of which, if any, components could be connected by Ethernet cable, for example, rather than wirelessly. It’s also possible to get dual band routers that run on both 2.4 GHz (GigaHertz) and 5 GHz and can handle both new and legacy devices.