Everyone with a business and a website wants their website to be prominently featured on the search engines. Pay Per Click advertising is one way to ensure that your products and services are found by people who are searching for information related to those products or services. Google is one strong example but not the only example. Social media outlets such as Facebook and Linkedin have entered the online advetising fray.
For example, if someone is searching for topics of "best 4G phone"; on the left side of the page's results will be a list of websites and on the right side of the page will be a list of pay per click advertisements geared specifically to the keyword phrase "best 4G phone". On Google you can recognize these by looking the words "Sponsored" Link" in small print at the top of the advertising area.