What is Pay Per Click Advertising? What are Sponsored listings?
Pay per click (ppc) otherwise known as sponsored listings tend to appear at the top of the search engine or directory's results page, they also appear to the right of the "natural listings". These advertisements are available to buy on an auction type basis
As the name Sponsored listings suggests, the websites that appear within this part of the results are from advertisers who have paid to have their site listed on a particular search engine for a particular keyword or phrase which relates to their business.
Sponsored listings also known as Pay per click listings are based upon a bidding system. In simplistic terms this means that the highest bidder will be in the coveted number one position, the second highest in position two and so on.
For example below is a screenshot showing the bid prices on Overture (UK) for the key phrase "flights to LA"

This screenshot shows that www.expedia.co.uk is the highest bidder for this phrase, followed by www.ebookers.com and www.onlinetravel.com and www.deckchair.com.
The below diagram shows how the Overture sponsored listings are displayed on Yahoo UK.

As you can see.
How much you are willing to pay for a click determines where your companies advert will appear on the page.
What is a Click? Definition of a click
The definition of a click is when a searcher clicks on an advert and is redirected to an advertiser's website.