Gee weblink ... with your pro links in your sig, I would hope that you actually do know the diff for your clients sake ..
but lets play the game.
Article syndication is when you place duplicate content on another site such as an article site and people use it, but also include a link to your site for the privilege. Article spinning is for those who want original content, based on their own original article and dont trust people to syndicate properly or for other seo reasons.