Check engine

All modern vehicle have a computer or the ECM (Electronic Control Module) that controls the operation of the car powertrain. The main purpose of this is to keep the engine running at top efficiency w/ the lowest possible emissions.
Your car computer system has self-testing capability when the computer sense that there is a problem w/ some of the components it stores the correspondent trouble code in its memory and lights up the "check engine" or "service engine soon" to tell you that there is a problem and needs to be looked at.
Bring your car to the dealership or any reputable garage(shop)to hook up the scanner to the car computer to retrieve the stored trouble code(s).