Make Your Book More Discoverable with KeywordsHere is link to this Help Topic:
To increase your book's discoverability on Amazon, you need descriptions and keywords that accurately portray your book's content and use the words customers will use when they search. Along with factors like sales history and Amazon Best Sellers Rank, relevant keywords can boost your placement in search results on Amazon.com.
Once there at the Amazon self-publishing Help Topic, you'll find a summary of useful keyword types, metadata tips, what NOT to include when tweaking your keywords, as well as this link to Metadata Guidelines:
You'd be wise to carefully read this section and apply these tips to help readers find your self-published work. My experience is that keywords are probably the #1 way search engines and Amazon Marketplace search features help a reader find my ebook and paperback books. Great info to bookmark and refer to often.