doddsredoubt: basically, if you want wireless internet, then you'll need a device to send the internet signal from your phone line, and you'll need a device to receive the signals. the box that sends the signal is the wireless router (make sure you get the right sort -- just a router, or one with an ADSL modem).
you also need something to receive the signals... some laptops (many, now) come with this receiver built-in. older laptops and especially desktop PCs don't have this, so you need to buy a receiver that just plugs into the back and lets the laptop or PC get the wireless internet signal. this is the 'dongle' wideboy talks about.