The Cubase Generic Remote is designed to allow you to connect virtually any device to Cubase to use as a control surface.
All it basically does is provide you with a way to take incoming controller information, and tell Cubase what to do with it. For example, you might set the Generic Remote to look out for controller number 44 on MIDI channel 13, and when it receives it, use it to control the fader on MIDI track 3 in Cubase.
Usually you set up a whole bank of controls, such as the faders or knobs on your keyboard, or the sliders on a dedicated control surface. And a single Generic Remote template can be used to map the controller data from several external devices (although you may want to set up seperate Generic Remote's for each device for clarity).
Below is the template I put together for use with the Alesis Photon X25. If you've got a Photon, then feel free to download it and put it to use. If not, then please feel free to use it to get to grips with the whole Generic Remote thing if you so wish.
To use it, just choose 'import' from a new generic remote device. I have my default project set up with 10 audio channels and 10 MIDI channels, so they are immediately controllable from the Photon's panel. The buttons on the Photon are assigned to control the sequencer transport, mapped as the symbols on the Cubase card inserts that come with the keyboard.
It's also important that you use the default controller assignments for the Cubase LE preset on the keyboard. It's this setting that determines which MIDI controller number the keyboard generates for each knob and button. So if you alter this from the default, Cubase won't know what to do with those controllers when they are received.
If you have altered the preset, you can re-teach Cubase which controller to look out for. You do this by twiddling the knob or button concerned and then clicking 'learn' whilst you have the line for that knob/button highlighted in the top half of the generic remote device panel.