Amazon offers content creators with seven boxes in which we can enter our target keywords. In each box, we can use up to 50 characters.
These keywords are extremely important, because the Amazon search engine is so dumb that it won't index your book content and description!
Apart from book author names, title and subtitle, users can only find your books by searching keywords in the 7 x 50 charactor spaces. Categories won't help in most cases
"The Conquest of Gaul" by Julius Caesar For example, if you leave the keywords empty, it won't show up when readers search "war".
Please correct me by submiting new issues, if Amazon has made any changes.
So, this tool was design to put as many keywords as possible to maximise the utility of the 7 x 50 charactor spaces.