Localization is adapting an app's store listing — metadata, screenshots, and keywords — to a specific language and market so it ranks and converts in that audience's own language.
Localization is more than translation. A properly localized listing uses the keywords people actually search in that language (which are rarely literal translations), screenshots with translated captions and culturally relevant framing, and a description written for how that market evaluates apps. On the App Store, each localization carries its own metadata set; on Google Play, you add localized listings per language. Done well, localization lifts both discovery and conversion in the target market.
Localization also unlocks the App Store's cross-localization mechanic: because some storefronts index the keyword fields of secondary localizations, adding a localization can expand your keyword coverage even in markets where users speak another language. The strategic question is always which markets justify the effort — a funded startup expanding into Brazil, Japan, or Germany usually sees the strongest return from full localization of the highest-traffic storefronts first.
Example
A meditation app entering Germany doesn't just translate "sleep" to "Schlaf" — it researches that Germans search "einschlafhilfe" (falling-asleep aid) and builds the German keyword field around the terms with real local volume.