Can someone explain the American voting process to me?

Pretty much the whole thing. I'm really interested but have no idea what they mean by "electoral" and such....and why someone who wins the popular vote may not win the election? Please explain in the simplest way possible, thanks! Perhaps someone could explain this little diagram too: a href="http://news.yahoo.com/election/2008/dashboard"http://news.yahoo.com/election/2008/dash…/a