What does the timing belt do in a car..?

I have a 92 model automatic civic fuel injected i seem to be faced with a trimbling problem with the engine during driving....the engine acts as if it's straining to pull the car....what i did i put the car on park & rev the engine hard & what i heard was the same stifling noise from the engine.....my mechanic... show more I have a 92 model automatic civic fuel injected i seem to be faced with a trimbling problem with the engine during driving....the engine acts as if it's straining to pull the car....what i did i put the car on park & rev the engine hard & what i heard was the same stifling noise from the engine.....my mechanic told me it could be my timing belt....i would like to know if the "timing" is OFF could this be responsible for the trimbling of the engine..?
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