PPC stands for pay-per-click, a model of internet marketing in which advertisers pay a fee each time one of their ads is clicked. Essentially, it's a way of buying visits to your site, rather than attempting to “earn” those visits organically. Search engine advertising is one of the most popular forms of PPC.
Cost per click, which usually goes by the acronym of CPC, has two different meanings. For a search engine, the term cost per click means how much the search engine charges advertisers each time a visitor clicks on a sponsored link. Cost per click can also mean the total cost accrued by the advertiser when the ad is clicked on, from just listing the ad to the additional cost of the click-through on the part of the visitor.