In catalogs and publishing, an index is a list or database of topics or products linked to their locations. Amazon indexes keywords so that when a customer types in a search term, Amazon’s search engine is able to locate relevant products and publish them on a results page for customers to see.
In order for a product to appear in search results for a searched word or phrase, the product must be indexed by Amazon for that word or phrase. Ways that sellers try to get words for their products indexed is by including them in product titles, bullet points, and descriptions, as well as in the product’s backend data. Products also get indexed for words through PPC.