This book does not explain HTML and will not tell you how to create or modify web sites. To put the concepts and software explained into practice, you need to have basic knowledge of web fundamentals and skills or to work with a webmaster who does.
To profit from Part III you need, of course, a service or product to advertise that makes you money, but webmasters who are simply interested in monetizing the content of their own sites, and not in advertising per se, will gain from an understanding of "how the other half lives." An interesting idea to explore is to see if you can profitably drive traffic to your site using AdWords and make more revenue from AdSense and other programs than it costs you to get the traffic.
Part IV, Using the AdWords APIs, is written for programmers and assumes an audience that has a basic understanding of the web services mechanism, already knows how to program, and can sight-read code (in PHP or C#, depending on the chapter).