Google Adwords also referred to as Paid Per Click
Through the Google Adwords platform many types of ads can be created. In search engine results pages (SERP) the top listings (often first three) are paid text ads. Text ads can also show on affiliate sites and partner sites. Youtube commercials are submitted through the Adwords platform as well as display and banner ads.
Although these ads directly cost money, they can be extremely effective. They occupy the top positions and they are immediate. The Adwords program is also completely measurable so tracking Return on Investment (ROI) is much easier then any other advertising medium.