Pay Per Click
Pay per click (PPC) is an advertising model used on search engines, advertising networks, and content websites/blogs, where advertisers only pay when a user actually clicks on an ad to visit the advertiser's website. Advertisers bid on keywords they predict their target market will use as search terms when they are looking for a product or service. When a user types a keyword query matching the advertiser's keyword list, or views a page with relevant content, the advertiser's ad may be shown. These ads are called a "Sponsored link" or "sponsored ads" and appear next to or above the "natural" or organic results on search engine results pages, or anywhere a webmaster/blogger chooses on a content page.
Pay per click ads may also appear on content network websites. In this case, ad networks such as Google AdSense and Yahoo! Publisher Network attempt to provide ads that are relevant to the content of the page where they appear, and no search function is involved.
While many companies exist in this space, Google AdWords, Yahoo! Search Marketing, and Microsoft adCenter are the largest network operators as of 2013. Minimum prices per click, often referred to as Costs Per Click (CPC), vary depending on the search engine, with some as low as $0.01. Very popular search terms can cost much more on popular engines. Arguably this advertising model may be open to abuse through click fraud, although Google and other search engines have implemented automated systems to guard against this.