It is important to understand the basics of search, including the difference between paid and unpaid search, before starting any SEO campaign, especially a campaign that has both paid and unpaid elements.

Terminology To Know:
Organic: Un-paid search results
PPC: Pay-per click
SERPS: Search engine results page

Pay-Per Click Results:
PPC results are advertisements.  If you run a PPC campaign, you pay everytime a user clicks your ad and follows it to your website.  You usually choose relevant search terms to bid on, and your ad is displayed when a user searchs that term within Google, Yahoo, or other search engines. PPC results are displayed above and to the right of organic listings in both Yahoo and Google.  Google calls these ’sponsored links’ while Yahoo uses the term ’sponsored results’.

Organic Results:
Organic listings are un-paid results that are typically displayed in the main column of the serps.  These results are ranked by a number of factors used to determine their relevance to the search term.  Some of these factors include: keyword density, title tag relevance, incoming links, Google Page Rank and meta tags.  Organic results can contain map results, product results, blog results and video results.

The Above Image Shows How Google Displays Organic & PPC Results