Pay per click in search engine advertising, the advertiser would typically bid on a keyword so the PPC rate changes. SEO refers to optimization of web pages so they would do well in organic search engine queries. An organic search engine query entails typing in a keyword or a keyword search phrase into the search bar so that the search engine can search through their indexed pages and return those that are relevant to the keyword used in the query. Pay per click advertisements are usually text ads placed near search results; when a site visitor clicks on the advertisement, the advertiser is charged a small amount.