Google Adwords does this by using the placed text ad that appears when someone searches for phrases that are related to one's products and services - and they ultimately display as a sponsored link. The way Google Adwords works is under a pay per click basis and you only pay the amount per person clicking on your ad (that you have initially bid for per click) as a result of a web search.
These ads are in text format and consist of a title line followed by two short descriptive lines afterwards and additionaly have a URL link to a website or a specific website page.
These ads will be shown on results page that the customer wants them to appear in.
Here is a process model showing Google AdWords from the customers perspective that I have created:
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