Keyword match types (broad, phrase, and exact) control how closely a search must relate to your keyword before your ad can show. They are the main lever for balancing reach against relevance on Google Search.
The three types
Broad match shows on related searches, including ones that share intent but none of your words, and leans heavily on Smart Bidding to stay efficient. Phrase match requires the meaning of your phrase to be present. Exact match shows only on that search or its close variants. Reach falls and relevance rises as you move from broad to exact.
Match types need negatives
Broad match without tight negative keywords and a good conversion signal drifts into junk traffic fast. The search terms report is where you see what each keyword actually matched and prune it. Modern broad match paired with Smart Bidding can work well, but only with clean conversions guiding it.