Match Types (Exact vs. Broad) are the two Apple Ads keyword settings, broad and exact, that decide how closely an App Store search must resemble a bidded keyword before the ad can show.
Apple Ads offers two match types for search results keywords. Broad match, the default for new keywords, runs the ad on relevant variants of the keyword and related terms: singulars and plurals, misspellings, synonyms, related searches, and phrases that include the term fully or partially. Exact match, entered in brackets as [keyword], gives the tightest control: the specific term plus variants Apple's systems judge close, such as misspellings, reordered words and translations. A keyword's match type can't be changed once it's added; you pause it and add it again. Negative keywords use exact match by default.
Match types are the backbone of campaign structure. Apple's recommended setup runs brand, category and competitor campaigns on exact match with Search Match off, so spend and performance map cleanly to the terms you chose, and puts broad match in its own ad group within a discovery campaign whose job is to surface new queries. The Search Terms report then shows the real searches those broad keywords matched. For ASO, exact-match data is the cleaner read on whether a keyword converts before you spend scarce metadata characters on it, while broad match finds the phrasing users actually type.
Example
A photo-editing app bids on [photo editor] in an exact-match category campaign and on photo editor as broad match in a discovery campaign. The broad keyword surfaces "collage maker for photos", which converts well, so the team adds it as a new exact-match keyword and considers it for the subtitle.