When creating your Advertising Campaigns, you can decide if you want to create an automatic campaign, manual campaign, or both.
Keywords: Amazon decides which keywords the Seller's ad will appear for, based on the A9 Algorithm.
Keyword Match Types: Amazon chooses the match type for your ad.
Negative Keywords: Amazon chooses the negative keywords for your ad.
Pros: fewer management efforts.
Cons: imprecise ad targeting.
Keywords: the seller will create the sets of keywords for which he wants his ads to appear on.
Keyword Match Types: sellers can choose what match type to use for their ad (exact, phrase, or broad).
Negative Keywords: sellers can choose which keywords to add to their Negative Keywords.
Pros: precise ad targeting.
Cons: more effort required for the manual management.
Manual campaigns give more accurate results, thanks to the ability to optimize keywords and the precision in ad targeting. While with the automatic campaign, Amazon decides which keywords are relevant for your product.