: This is usually a usb adapter that allows a hard-wired desktop to become 'wireless'. The wireless adapter communicates over 802.11x and acts as a network card for your desktop. This can also be used for a notebook.Wireless Access Point
: AP is usually used when you already have a router and just need a way for wireless clients to connect to the network. AP does not usually feature a DHCP server or firewall and other fancy features of router.Router
: This allows you to share your cable/dsl broadband connection with one or more computers. This has a DHCP server,firewall, print server etc.Wireless Router
: Same as a hard-wired router but now also incorporates an Wireless Access point along with Wireless Security mechanisms like WEP, WPA etc. Since these run at same frequency (2.4Ghz) as your cordless Phone and microwave, be ready for interference.
Wireless Router is usually the way to go. I have a regular desktop and a 9100. I use a D-Link DI-624 router. My desktop connects to router via a Cat5 cable. Read my previous post here
This might help..Home Wireless LANs Installation Tips