Definition: Sell more stuff to more people for more money more often. —Clark Parker
Excursus: Where does the role Software Product Manager ends? In my opinion when he has deployed a Software that respects the limits and goals of the Business Requirements. Depending on the size of your company and/or team you might have a person (or an entire team) dedicated solely to marketing. Whether or not you will be the person in charge of Marketing, the Software Product Manager should know the basics of Marketing.
Study note: This section does not try to be an exhaustive collection of resources on Marketing. Marketing is such a big and broad discipline that would require a whole Marketing Stack. Well, in fact, it exist! See below. This section tries to give the very basics knowledge of Marketing, more specifically Web Marketing.
Why study for this certification? Google Adwords is an advertising product that allows you put ads on Google. It is the world leader in Demand Harvesting advertising. In plain words, gives the ability to have exposure when the user is looking to buy something, Google. In my opinion is very important to know how Google AdWords works even though it is not you main advertising channel, because all the other advertising channels can be benchmarked to Google Adwords and because all other advertising Channel have a price structure that is somehow comparable to Google Adwords.
Why study for this certification? If your product will be marketed mostly on the web, you have to have a basic Search Engine Optimisation knowledge. For 2 reasons: