To ensure that the most relevant products are shown at the top of search results, Amazon uses a variety of search algorithms and techniques.
Before getting into details, let’s start with a brief explanation of 2 of the most used targeting options
Phrase match means that your ad will be shown when someone searches for your keyword phrase, in the exact order you specify, with additional words before or after it. For example, if your phrase match keyword is "black shoes," your ad may be shown when someone searches for "black shoes for men" or "black shoes on sale," but not when someone searches for "shoes black".
Exact match means that your ad will only be shown when someone searches for your exact keyword, with no additional words before or after it. For example, if your exact match keyword is "black shoes," your ad will only appear when someone searches for "black shoes" and not "black shoes for men" or "black leather shoes".
While Exact Match can be a powerful tool in driving targeted traffic to your products, there have been reports of strange behaviors associated with an exact match on Amazon:
One issue is that the exact match targeting option may not always display ads for exact matches. This is because Amazon's algorithm may also consider "close variants" when determining which search terms to display ads for. Close variants may include singular or plural variations, misspellings, synonyms, and related terms. This can lead to ads being displayed for search terms that are not actually exact matches, which can be confusing for advertisers.
Other times, it seems to be displaying ads for irrelevant search terms and wasting an advertiser's budget. For example, in a recent Amazon search term report, the exact match on “umbrellas for rain” made impressions (very few) on “amazon fire stick remote”, also “aesthetic highlighters” made some for “lunchbox”.
Query Classes
Astra technology uses a tool called Query Class which is a group of related keywords or phrases with the aim to learn how Amazon's "Exact matching" is done between query(ies) from a user and a keyword purchased by a seller.
That is why on some occasions, ads have been displayed to users who did not actually enter the intended search query, but rather a similar query that was classified in the same query class. For example, if a customer searches for "swimmers cap women" or misspellings like "swimmers cap womens" the query class algorithm will relate both with "swimmer cap for women"
The combination of exact match and query classes aims to provide more relevant search results. However, rest assured about the misleading behavior of the exact match, it makes less than 0,1% of the total impressions.