MAN is short for metropolitan area network. Such a metropolitan area network typically connects many computers and covers a city, larger company or university campus. It is usually capable of broadband communication and may be hosting other applications as well, such as telephony. This computer infrastructure may nowadays be based on optical fiber, but still also on a lot wires.
As opposed to this, a WMAN, or wireless metropolitan area network, is based on wireless communication methods and uses part of the radio spectrum. Some parts of this spectrum are licensed, others are available for the use by the general public. As opposed to the small areas covered by a local area network (LAN) or its wireless companion (WLAN), a WMAN covers a much larger region and has some potential to replace more traditional mobile communication networks. In particular, WMANs could serve as a future, alternative way to carrier-based networks.
In particular, WMANs are a wireless replacement for the (in)famous last mile, a so called wireless last mile approach to bypass the often monopolistic fixed network local loop while even offering broadband possibilities.
The initiative for wireless metropolitan area network specification activities seems to be more on the American side of the Atlantic Ocean with the IEEE (and US communication industry) as the driving force behind it. Perhaps this is an "answer" to the European success of GSM while some Europeans seem to think they may rest (in peace) with UMTS. However there is also ETSI HiperMAN, the corresponding standard of the European Telecommunications Institute, and developments are done in cooperation with the IEEE and the WIMAX Industrie Forum, an industry club to promote the advancement of the technology strongly supported by chip manufacturer Intel.
While IEEE 802.11 specifies the radio technology for 802.11 (WLAN) hotspots, 802.16 (ETSI HyperMAN) specifies the technology for WMAN technology. The standard will help accelerate the introduction of wireless broadband by delivering the desired enabling infrastructure tools to wireless service providers. This allows them to compete with the traditional fixed network monopolies or to reach out to places where such infrastructur did not exist before. The basic IEEE standard was originally intended for fixed stations only but is now moving towards at least slow mobility (as opposed to GSM-type mobility which supports relatively high speeds of a user craft.). Also meshed topography networks are future options.