>"affect" is a verb; "effect" is a noun.
It really isn't quite that simple. Both words can be used as either noun or verb (though the use of 'affect' as a noun is rare, and somewhat obsolete).
A man may effect a change, but a change can affect a man. A man may also affect a change (i.e., pretend). I cringe every time I have to use either word, and sometimes reword things so as to avoid having to pause to think about which one to use to achieve the desired affect... er, effect. I think.