Hi,
Wired XBox360 Controllers connect to the USB port. Wireless XBox360 controllers for Windows come in 2 parts 1. the wireless controller and 2. a small rectangular shaped receiver/transmitter that plugs into the USB port.
If you are planning on getting a controller make sure of the following:
1. Get Microsoft brand,
2. when looking at Wireless, make sure it says XBox360 controller for Windows (the one for the XBox360 doesn't have the little transmitter/receiver, and
3. Make sure it is XBox360 not XBOX. The older controllers for the original XBox do not work with my plugin.
Hope that helps.
Lee