The light ON/OFF is on what they mean and can affect my car if they still on and how i can turn off.
Post a photo of the light so we can see and understand what you are referring to...
It means OverDrive was turned off. Overdrive is the final gear in your transmission that allows you to save gas on the highway. You can turn OverDrive off if you need extra pick-up to pass someone on the highway as it will force you into a lower gear with more torque. The Overdrive button is likely on your automatic gear shifter. Unless you turn it back on, you are wasting gas on the highway for no reason, but it won't really effect low-speed local travel.
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