App indexing is something Google and Apple are both looking to get perfect. This article dives deep into the specifics of how Apple's indexing algorithm can make or break an app.
Apple’s ability to mine iOS user engagement metrics allows them to make engagement a central part of the ranking algorithm, putting less emphasis on traditional ranking factors like titles and descriptions. This is a notable evolution from how Apple currently handles search in the iOS App Store, which relies heavily on titles and keywords to determine app ranking.
http://searchengineland.com/app-indexing-new-frontier-seo-apple-search-ios-app-indexing-223880