The document introduces the Salesforce Mobile SDK for iOS. It provides tools for building native, hybrid and HTML5 apps on iOS and Android platforms. These tools include OAuth2 for authentication, API wrappers to interact with Salesforce REST APIs, an app container to embed HTML5 apps and access device functionality, and secure offline storage. The document also discusses device usage trends, the REST architecture, and provides instructions for installing and using a sample mobile app built with the SDK.