Amazon has special categories that are designated by assigned keywords for select genres. If your book is in those genres, using a designated keyword is the only way to get listed in the special categories. The video explains it all, and more info can be found by searching the term "Make Your Book More Discoverable With Keywords" or by visiting this link: https://kdp.amazon.com/help?topicId=A2EZES9JAJ6H02

Amazon rankings for categories show on the product page when a book is in the top 100 for sales in a specific category. Sometimes these are the categories you've chosen, while other times they are assigned by Amazon. In either case, category ranking and where your book shows up in results after a keyword search for that category are two different things (i.e. if you type "romance" into the search bar, the top results aren't necessarily the top books in the Romance Category; they are just the books doing best for "romance" as a keyword).

Since Amazon’s search bar does not give exact numbers on often a term is searched, it’s wise to check terms and similar phrases with Google's Keyword Planner to see if one word or phrase is more popular than the others. Here is the link: https://adwords.google.com/ko/KeywordPlanner/

It's time to begin your preliminary keyword list with idea for words and phrases related to your book. Think of terms that might get typed into Amazon's search engine that involve subject matter and themes, genre and story tone, character types and setting.

Testing your keywords individually at Amazon will give more information on the wisdom of each choice. Remember to look for drop-down selling-prompts, total number of results listed and how many appearing books in the results contain the keyword (or keyword phrase) in the title or subtitle.

Here are examples of cross-testing keywords at Google's Keyword Planner and back at Amazon. Ask yourself if the search results are enormous or very small, get a sense for the competition level, and also try ways of writing the same thing with similar terms to check them. This will give more data than just checking at Amazon's search engine alone.

It's wise to double-check your keyword choices before implementing them in your title, subtitle, KDP keyword and category selections, along with your description and actual book text.

Now it's time to add keywords to your title and subtitle with respect to Amazon's guidelines listed here: https://kdp.amazon.com/help?topicId=A294SHSUYLKTA6

Add your author name and any contributors (editor, illustrator, etc.) to your KDP Amazon book's description. Also fill out an Amazon Central Author Profile at https://authorcentral.amazon.com

Now it's time to add the 7 best keywords at KDP Amazon. Remember these can always be changed in the future and to press the "Save Changes" button.

As with the KDP keywords, the categories can be changed anytime in the future. Select relevant and specific choices. Sometimes Amazon will assign their own as supplemental to your choices, especially if you have keywords that match special categories as explained in previous lectures. Whenever making changes to categories (or any KDP detail), click the "Save Changes" button and Publish when ready.

Adding keywords to the description presently helps more with Google searches than at Amazon, but it's still wise. You can keep things reader-friendly at the top and add extra keywords to the bottom to make it search-friendly as shown in the lecture. Changes can be made anytime at either KDP Amazon or at Author Central, with the later being quicker to implement changes.

Books with their own ISBN, not just an ASIN, can sign up for the Search Inside or Look Inside feature to have their interior text indexed by Amazon's search engine. This way you can insert additional keywords into the front matter, preferably the copyright page or another page skimmed by readers. This is the link to sign up: http://www.amazon.com/gp/help/customer/display.html?nodeId=14061791