Affect is primarily used as a verb.
It means to alter the feelings of or change the mental state of something or someone; to influence; to change something or someone in some way.
As far as, to alter the feelings of someone, think of the word affection which is a feeling in itself.
Here’s an example of affect in a couple of sentences regarding this definition.
I will affect you with my passionate speech.
I wonder how the election will affect our course of history.
The movie affected her so deeply, it brought tears to her eyes.
Effect is primarily used as a noun.
It generally refers to the result of something, or the power something might have in order to get that specific result.
Now, here’s where it gets tricky. I can use this word in some of the same sentences as above.
The election will have a profound effect on the course of history.
The effect of the movie, brought tears to her eyes.
(To remember it as a noun, think of the phrase “special effects” used in movies.)
I know it all looks and sounds the same, but do you see how one is used as a verb and the other is used as a noun?
Now, very rarely, effect is used as a verb and affect is used as a noun.
Here’s some examples:
Johnson said the cutbacks were designed to effect basic economies for the company.
(I’ve personally come to find that if you can use effect as a verb, just replace it with a different word entirely.)
Affect as a noun is only used as a psychological term that refers to facial expression and/or emotional response.
A person suffering from catatonia is said to have a ‘flat affect’.
I hope this helps,
If not, ask her.