This is one of those strictly written errors in English; nevertheless, it’s still a grammar error. Affect and effect have several meanings, but people get them most mixed up when trying to use the noun effect as the verb to affect. Stay with me; it gets much easier.
Affect is a verb. When you affect something, you influence it (verb) or change it (verb), as in the following sentences:
- Grammar affects my life.
- Cheating in the presidential race affected the outcome.
- That decision will affect our profit margin.
The use of effect is usually as a noun meaning an influence (noun) or a result (noun).
- Grammar has an effect on my life.
- The cheating in the presidential race had an effect on the outcome.
- The decision had the effect of increasing our profit margin.
Effect can be a verb also, but it isn’t used often; it means to bring about.
- The new CEO effected change in the company.
Sherry
Paul’s book–Literally, the Best Language Book Ever;
Everything Language and Grammar 