Competition Score for Keywords
The Score you see attached to a Keyword is the "Competition Score" and it reflects what extent the Keyword is deemed to be competitive on Amazon - a D score on a Keyword means that keyword is extremely competitive and that it's probably very hard to rank on page 1 for it, while the opposite holds true - an A score keyword means it's probably quite easy to reach page 1 for that keyword.
This score is based on a set of parameters such as the Reviews and Ratings of the competing products that are ranking for that keyword. Hence, it's a quick indicator of knowing how hard it is to rank for a Keyword.
Competitiveness Score for Products
Similarly, the Score you see attached to a product is the "Competitiveness Score" and it reflects to what extent the Product is deemed to be competitive on Amazon - a D score on a Product means that product is really behind competition and that it will theoretically struggle to rank at page 1 notably due to its rating and number of reviews that might be lagging behind competition.
Our proprietary algorithm for computing it currently heavily relies on the Average Price, Average Number of Reviews, and Average Ratings of the competing Products, especially those that are ranked in the first pages for the product's relevant Keywords.
To compute those scores, we need to have sufficient data on the Product and Keyword, including a minimal number of reviews for the Product. If data is lacking, the scores won't show up.