Keyword Relevance is how closely a search term matches what an app actually does — a core input to store search ranking, and the reason an off-topic ranking rarely turns into installs.
Relevance has a mechanical side and a human side. Mechanically, Apple bases App Store search results partly on text relevance — matches in the app's title, subtitle, keywords and primary category — alongside user behavior such as downloads, ratings and reviews. Google Play draws on listing text such as the title and descriptions, and its metadata policy says to avoid "repetitive or unrelated keywords or references." Apple lists terms not relevant to the app among the improper keyword uses that commonly cause rejection, and guideline 2.3.7 asks for keywords that "accurately describe your app." The human side is whether someone who taps the listing finds what the query promised.
An irrelevant ranking is a poor trade even when it's achievable. Shoppers who searched for something else scroll past, so impressions rise while conversion falls — and because Apple counts downloads among its behavioral signals, in our experience such positions are hard to hold. Apple Ads applies similar logic to paid search, cautioning that keywords should be relevant to what the app offers or the ad may be unlikely to win the auction. Practitioners judge relevance with a simple test: would a person typing this query be glad to find the app, and do the first screenshots prove it within seconds? Terms that fail go, however popular.
Example
A language-learning app could become eligible for "translator" by adding it to its keyword field, but those searchers want instant translation, not lessons, and they skip the listing. Swapping it for "vocabulary practice" brings fewer impressions yet more installs, because the listing delivers exactly what that query asked for.