Hi There I just wanted to add that as the others have commented - PPC means 'pay per click' which is a marketing channel and Adwords is the Google specific offering of this marketing channel. In addition - SEO (search engine optimisation) is a completely seperate discipline - although closely related as both PPC and SEO search results are displayed on the same page. The management of the two, however, is very different as PPC is paid for and SEO is all about optimising your onsite and offsite content and site structure to better position you in the search engines free listings.
Adwords actually allows advertising in two different ways. One way is PPC - where the advertiser agrees a maximum amount they are willing to pay for each click or visitor sent to their offer. Adwords also allows you to advertise to the content network using PPV or pay per view. Then the advertiser pays Google up to a maximum amount for each 1000 times their ad is displayed - irrespective of whether the ad generates any clicks or not.
ppc is a category. adwords is in that category, along with bing, adbrite, and lots of other smaller companies. none of them have anything to do with seo.