How is this a PM question? I would have taken it in a complete different direction as I know the ads world better. When you enter a url in the browser, the site makes an ad-call to the SSP which then converts it into a bid request. The bid request is sent out to the DSP partners who then run the auction based on the metrics available in the request (user cookie, IP, demo , audience segment etc). The winning ad is then sent back to SSP in the form of bid response who then runs the auction again between all the winning ads it got from the DSPs. The ad which wins finally on the SSP side is shown to the user on the site/ url the user entered. I am failing to understand what skills this type of question is gauging?