App Store keywords
The 100-character comma-separated field in App Store Connect that tells Apple which search terms your app should be considered for.
App Store keywords live in a single 100-character field, entered once per localization and comma-separated with no spaces. Apple also indexes your app name and subtitle, which carry more weight than the keyword field itself — so the name is the first keyword decision you make, not the last.
The field is where most of the wasted characters are. Spaces after commas cost you characters for nothing. Repeating a word that already appears in your app name or subtitle is redundant, because Apple combines indexed terms into phrases on its own: with "sleep" in your title and "sounds" in your keywords, you are already eligible for "sleep sounds". Plurals are handled, and category names are indexed automatically.
Each localization gets its own 100 characters, which is the part teams underuse. Adding a localization you barely translate still buys you another keyword field that Apple indexes for that storefront.
What keywords cannot do is convert. Ranking for a term brings someone to your product page; whether they install is decided by the screenshots and the first three lines of the description. Teams that plateau on ASO have usually optimized the half that is measurable and left the half that is visual untouched.