Bridging connections means using your computer to merge two distinct networks and make them seem as one contiguous network.
For example, you have a laptop that is connected wirelessly to a LAN and using a wire to a WAN (let's say, to your office so that you can telecommute).
Now, you want all your computers on your LAN to become part of your WAN, but want them to retain their wireless functionality.
What you can do is "bridge" the two networks. This will create a virtual network adapter that will subsume the ethernet/wireless adapters on your laptop. This is all demonstrated a lot easier by an example. I am using LANx for your LAN computers, same for WAN, and LTP for your laptop. Numbers shown are IP addresses:
LTP: 192.168.0.10 (wireless)/188.8.131.52 (wired)
Now, let's say you bridge the networks. The new configuration will be as follows:
LTP: 184.108.40.206 (bridge)
As you can see, now all the addresses are on the same subnet. All the LAN computers will be able to see the WAN computers, and vice versa.
Bridging is commonly used as an alternative to IP routing, the latter of which I can attest is a pain in the a** on Windows.
EDIT: Working example: http://www.microsoft.com/windowsxp/u...02april22.mspx