On some (newer) bikes there is a map switch with two settings. One setting has the sun as symbol, the other setting has cloud with a rain shower.
This switch is often placed on one of the radiator hoses, out of harm's way. It may be on the handlebar, but then its gonna break.
here is an image from my own 06 200.
In the "rain" position, the ignition is adjusted in a way that makes the engine a little slower / less powerful and peaky, perhaps better for slippery conditions.
In the "sun" position you get full power.
But if your bike isn't jetted correctly, you will hardly notice any difference. On my 06 200, however, the switch made quite a difference (when running with the Lectron carb).