A keyword is what you bid on; a search term is what the shopper actually typed into Amazon. Amazon matches search terms to your keywords according to the match type you selected, so a single broad keyword can collect hundreds of different search terms. Optimisation happens on the search term side — reading what you actually paid for, then deciding which terms deserve their own keyword and which deserve a negative.
A concrete example
You bid on the broad keyword 'water bottle'. The search terms you pay for might include 'insulated water bottle 1l', 'water bottle for kids', 'water bottle cleaning brush' and a competitor brand name. Only some are your product.
Judging that keyword on its blended ACOS hides everything. It may look mediocre while containing two excellent search terms and six that should never have been bought.
Why the distinction drives the whole workflow
Every core PPC routine sits on this split. Harvesting promotes profitable search terms into keywords. Negation blocks unprofitable ones from matching again. Neither is possible from keyword-level reporting alone.
The Sponsored Products Search Term report is where the two columns appear side by side. It is the single most useful export in the account.
Want this checked on your own account?
The free audit answers this question with your numbers instead of general rules — no Seller Central password needed.
Get my free audit