This document discusses how app indexing works to connect mobile apps to search engine results. It explains that app indexing allows mobile apps to be indexed and accessible via Google Search. It provides steps on implementing app indexing for iOS using Xcode and Firebase indexing, as well as for Android using Android Studio, Firebase, and Android App Links. The document emphasizes structuring app links to match website URLs and adding entitlements and files to connect apps to websites to enable app indexing.