Effect:
1. Something brought about by a cause or agent; a result.
2. The power to produce an outcome or achieve a result; influence: The drug had an immediate effect on the pain. The government's action had no effect on the trade imbalance.
Affect:
1. To have an influence on or effect a change in: Inflation affects the buying power of the dollar.
2. To act on the emotions of; touch or move.
The main differences of effect and affect are:
To affect something is to change or influence it, to effect something is a rather formal way of saying `to make it happen'. Confusingly, because either may produce an 'effect' or result this is a common error.