App Store Optimisation (ASO) improves an app's visibility and conversion rate within the Apple App Store and Google Play Store - it is the app ecosystem's equivalent of SEO for websites. ASO covers optimising the app title, keyword field, description, screenshots, preview video, icon design, category selection, and managing ratings and reviews. The key distinction from SEO is the platform: ASO operates within closed app store algorithms. There is no backlink building in ASO - instead download velocity, review volume, and update frequency are the dominant signals. App store visibility should be reinforced by social media marketing campaigns that drive initial downloads, since early download velocity is one of the strongest ASO ranking signals.