Pay Per Click campaigns are a way of advertising in specific words paying only for the clicks (and the visits) your site receives and not for every impression. Essentially search engine marketing is an alternative method to promote your site in search engines results, if you don't have the capacity and potential to push your pages in the organic results of a popular search engine like Google, Yahoo, or Bing.
If someone search on google with the word «website» search results is literally almost 1 billion. Since it is almost impossible for a simple site to be found in the first 10 results for highly competitive keywords, the owner of the site can create a PPC Campaign (like google adwords campaigns) and advertise on the first page of the selected search engine for the key phrase he choose. Using this form of advertisement, the site owner will not pay for the people who just saw his ad after a search, but only for the visitors who clicked on his adtext and arrived at his site.
PPC Advertising is a direct method of testing the response to new products and services, a company may offer. Advertised company can control costs accurately, promptly informed in real time about the results of the campaign. Using a PPC campaigns companies can target with great accuracy potential customers searching on the internet for something specific. This means that in a well made campaign, the ads only appear when a user and potential customer is looking for a product or a service that the advertiser offers.