Akin to SEO for websites, App Store Optimization (ASO) is for mobile phones. It pertains to increasing your online visibility on app stores for receiving higher downloads. Through ASO, you can benefit as your app is displayed on renowned app stores such as Windows Store, Blackberry World, and Google Play.
Just like websites are rated by search engines in SEO, your app is ranked by App stores on their search results page. If you gain high ranks in their charts, it is likely that higher number of people will download your app.