Google Adwords is a very good example for understanding PPC program. 
The Ads in text appearing on the right side shows how the Ads are run. This will be helpful to you if you do not have a Website and you want to promote the product at Google's site. When the people do a search in the Google site, depending on the keywords the relevant Ads are displayed. Running the Adword requires registration, but it is not free. You have to bid for the keywords and pay for the clicks if your Ad is clicked by any visitor. But by choosing the right keyword, with the cost-per-click option, you are only charged if people click your ads. You are not charged for the impressions. This means that every pound of your budget goes toward bringing new prospects to you. You can edit your ads and adjust your budget until you obtain the results that you want.
If you are not promoting your own product, remember that click means nothing for you, only the subsequent Sale brings you commission. So do an analysis for yourself on latest hot products available in the Market Place. What was hot few months back may not be so much in demand now. So do some research. You can get details of Google Adword programs under the Advertising link below the Google search bar in Google.com home page. Other popular PPCs are Yahoo Overture etc., Try exploring about how the Search Engines works,  you will master about the keywords and your web page Meta tags etc., but that is beyond the scope of this Website. If you want to simply master Adword techniques then get it here.