There are three kinds of keyword match types: broad, phrase, and exact:
· Broad Match
If you set your keywords to broad match, your ads will be triggered by searches that include your keywords, as well as by searches that include synonyms of your keywords, singular and plural forms, and other variants of your keyword. For instance, an ad associated with the keyword "shoes" may be triggered by searches for "tennis shoes", or "shoes" or "footwear." The advantage of broad matching is that it will expose your ads to the highest number of users. The disadvantage is that it is less targeted, so you may find yourself paying for low-quality clicks.
· Phrase Match
Phrase match is slightly more targeted than broad match. If you set your keywords to phrase match, your ads are triggered by searches that include your keywords in the search phrase. For instance, an ad associated with the keyword "shoes" may be triggered by searches for "shoes" or "tennis shoes" but not by searches for "footwear" or "shoe."
· Exact Match
Exact match is the most precise form of targeting. If you set your keyword to exact match, only searches for exactly that keyword will trigger your ad. For instance, an ad associated with the keyword "tennis shoes" will only be triggered by a search for "tennis shoes" and not by searches for "blue tennis shoes" or "shoes" or "tennis footwear."
This match type allows you to target customers with great precision, but may greatly reduce your ad's impressions.