Keyword match types determine which queries an ad can be shown for. Exact match targets the query and its close variants, phrase match targets queries containing the meaning of the phrase, and broad match targets a wide set of related queries, including those that do not contain any of your words. The boundaries between the types have shifted over time, and all of them now work with meaning rather than a literal string, so even exact match captures synonyms and typos. The practical consequence is that without regular review of the actual search terms, budget leaks into unrelated queries. A proven approach is to start narrower, monitor what the system matches to, and expand gradually, while maintaining negative keywords as a living list.
See also: Search terms report, Audience exclusion, Smart bidding (automated bidding).
