Thats the engine management light and it should really have the pound symbol on it cos it usually means its going to cost you some money.
It is best to have it looked at straight away because you could be doing long term damage to your engine (or it could be something very simple - mine came on and it turned out to be nothing more than a dodgy bulb behind the actual warning light!))
Dont do what Homer Simpson did and put some tape over the light hoping it would go away!
Unfortunately these engine lights can mean anything from it just needs a reset up to new engine. As Gary said the best thing is to get it checked out quickly.
As an example if a sensor is sending the wrong fueling info to the engine getting it looked at now would mean a new sensor. Getting it looked at later could mean that the incorrect fueling has now caused the catalytic converter to go (big money).