"effect" as a noun means "result",
but as a verb, it means "to cause" or "to bring about". For example,
"the invasion of Iraq effected a regime change" is also correct because the invasion brought about the regime change.
The subtle differences between the verbs "influencing" a change, and "causing" a change, can add to the difficulty of using affect/effect correctly.
And it gets worse, because "affect" can be a noun, too, meaning "a subjective feeling (not visible)":
"He carried the affect of a man who had only witnessed an unjust killing and yet somehow felt responsible for it."
It can also be yet another verb, meaning "to feign" or "to pretend":
"He would affect an interest in the homely rich girl as a tactic to increase his own wealth."
To summarize...
Common uses:
"to Affect", a verb, meaning, "to influence".
"Effect", a noun, meaning, "a result".
Occasional uses:
"to Effect", a verb, meaning, "to cause" or "to bring about".
Rare uses:
"Affect", a noun, meaning, "a (usually invisible) subjective feeling".
"to Affect", a verb, meaning, "to feign" or "to pretend".
And then there are the common catch phrases that have further new meanings:
"in effect" (in substance [but not literal reality])
"to the effect that" (having the meaning of [but not literally stated])
"personal effects" (personal goods or properties).
Unlike me, most people don't have the time to keep all that crap straight!