A bridge changes the type of media, in this case wired ethernet to wireless.
ie it connects at one side to a wired network, and the other side to a wireless. They are used in pairs. ie ethernet - bridge - wireless - bridge - ethernet.AP and bridge is completely different.
AP Client Mode - allows you to use the AP or router in this mode as though it were a, for example, USB Wireless adapter for a notebook computer or game system. In this case though, the Ethernet cable takes the place of the USB connection. A WRT54G or WAP in this mode allows for one wired client.
Network> AP >~~~Wireless~~~ <AP Client Mode --Client
A bridge is meant to serve as the role of replacing a wired uplink connection to another network/switch/subnet with a wireless link. You would have multiple clients behind this bridge. (Product examples are WET54GS5)
Network 1> AP > ~~~Wireless~~~ <Bridge --Wired--Network2/Switch -- Client1, Client2, Client3...
In essence, operating in AP Client Mode is a one client bridge scenario.
Now, something that combines the best of both worlds and adds in another feature is WDS - Wireless Distribution System. With a WRT54G or WAP in WDS mode, not only can you connect up to 5 wired clients and act as a wireless bridge, the AP will also repeat the wireless signal it is receiving and providing a range expanding effect. This does reduce throughput by half by having to repeat, but only on wireless clients connect to this WDS access point.
This makes me think we should start up a glossary of terms.
Question: What is Bridging Mode in Wi-Fi Networking?
Many Wi-Fi bridging mode products exist with varying levels of functionality.
Some wireless bridges support only a single point-to-point connection to another AP. Others support point-to-multipoint connections to several other APs.
Each AP in bridging mode connects to a wired LAN. Some AP models simultaneously support wireless clients while operating in bridging mode, but others work as "bridge-only" and disallow any clients from connecting. Some APs only support bridging with other APs from the same manufacturer or product family.
AP bridging capability (when it is available) can be enabled or disabled through a configuration option. Normally, APs in bridging mode discover each other viaMedia Access Control (MAC) addresses that must be set as configuration parameters.
While operating in bridging mode, wireless APs utilize a substantial amount of bandwidth. Wireless clients on bridged Wi-Fi networks generally share the same bandwidth as the bridge devices. Therefore, clients tend to perform slower in bridging mode than otherwise.
In Wi-Fi, repeater mode is a variation on bridging. Rather than join multiple LANs, repeater mode is intended mainly to increase the range of a single wireless LAN by extending the same wireless signal.