Let's say for example I have a website dedicated to cars, and on that site I put a few pages about motorbikes. Would those pages automatically display ads about Motorbikes? or Cars? is there a specific way to force the ads to display only ads on a particular topic? What method do Google use to determine the relevancy of their adverts?
Explained simple the ads will be targeted to the content on the actual page, not website. Cars content cars ads, bikes content bikes ads. Simple. You can manipulate them but it's not ethical and not advised in the same time.