Not directly. Google's computers place the ads. However, you can influence the ads. The ads are context-relevant to your webpage. If the page is about lions, the ads are about lions. If the page is about mountain lions, the ads are about mountain lions. And if the page is about the mountain lions of Palo Alto, then the ads are about mountain lions in Palo Alto. The more specific your page, the more specific the ads will be.

This means you can create informative, expert webpages on topics that have high value, and then add Adsense. These keywords will have high bids. You will make money from those pages.

For example, mesothelioma is a disease caused by asbestos. The asbestos class action lawsuits are in the billions of dollars. Law firms pay $160 or more per click to find people to join the class action. The law firm will earn hundreds of millions. The same for keywords that have to do with legal services for large companies, corporate banking and financing, home loans, and so on.