Ads are common on Google, the first listings are usually advertisements for businesses. Every time the ad is clicked there is a fee for the business. Pay-per-Click is efficient for businesses because it allows them to bid for ad placements on certain keywords. A fee might seem like a bit much, but a visitor to your site quickly turns into a customer which is worth far more than the fee.
Google AdWords is easily the most popular Pay-per-Click advertising platform, used by millions of businesses. Google starts auctions based on certain keywords the business with the best fit for the search is inserted into the ad spots. Businesses also receive a quality score that is combined with their bid to determine how high they will rank on advertisements.