• Wireless Access Points (APs): Wireless Access Points (AP) interface with your existing network via a 10BaseT Ethernet connection on the LAN side, and attach with wireless clients on the wireless side -thereby making them part of that subnet of your network. It must be noted that APs do not provide any routing/sharing capabilities, and most APs cannot communicate with other APs.

  If you all you want to do is to connect two of your machines over the air, you can get by without using an AP. You can do so by configuring your Wireless Network Adapter Cards to operate in peer-to-peer (AdHoc) mode -without having to go through an AP.

• Wireless Routers: If you need to route your data across network boundaries (e.g between your local Ethernet subnet and the Internet, or between two disjoint segments of your LAN), you would need a router. If you do not have a router on your network already, your least expensive option may be to get one of those Wireless Routers that double as both -an AP and a Router.
  
• Wireless Bridges: Most Access Points support communication only with wireless clients within their range, and not with other APs. Therefore, you can not simply use a couple of APs to wirelessly interconnect two non-wireless LANs. You would need to use a Wireless Bridge to do that. Traditionally, most wireless bridges support only connectivity between two network end points, and not with wireless clients. WLAN bridges allow several methods for bridging two networks: Point to Point (Master / Slave), Point to Multi-Point, Master plus AP, and the best of all -a wireless bridges that operates in Repeater mode. Most repeaters allow AP-to-AP bridging, while also allowing simultaneous multiple wireless client to AP connectivity.

Sometimes, the above distinctions may not be so clear though. For example, consider the following: A wireless access point (AP) is actually a layer-2 bridge considering it stores and forwards frames between the wired LAN on one side, and the wireless LAN segment on the other side. In light of this, it would not be incorrect to think of an AP as a two-port bridge -having one of its port connected to a wireless hub on one side (broadcasting/receiving data-packets to and from all it's wireless clients), and the other port bridging the same to the wired LAN.