Wireless networks based on IEEE 802.11 specifications are everywhere these days, and it's easy to see the benefits this technology brings to laptops and PDAs by providing mobility in many different forms. However, wireless networking can also be used to overcome various cabling challenges for clients that are still connected to a switch or hub via wires.
There are many instances, such as in historic buildings, where you can run wires in a room, but not between rooms or between floors. Other examples are large rooms like those in convention centers, where you have a lot of people walking about. Another example is in a factory or warehouse, where you may have a group of computers more than 300 meters away from the closest switch.
In each of these cases, it may be easier and less expensive to extend the LAN via wireless bridging, than to put wireless cards in all the computers and connect to them via a WAP. This is accomplished by placing a switch or hub in the remote location, and plugging a wireless bridge, or a WAP that supports bridging into that switch. The bridge then communicates with another bridge that is connected to the rest of your network. The ethernet ports on each bridge will be in the same IP subnet.
In essence, bridging is a tool for extending your backbone, and most of the bridges on the market have all the features you would expect for an enterprise environment, like support for Spanning Tree and such. But for smaller settings, like SOHO, there are some easy to use and very cost-effective bridges, that are practically plug and play. An example of this is Linksys' WET54G.
Tom Lancaster, CCIE# 8829 CNX# 1105, is a consultant with 15 years experience in the networking industry, and co-author of several books on networking, most recently, CCSPTM: Secure PIX and Secure VPN Study Guide published by Sybex.