Chapter 2, Leveraging Platform Features, provided a good overview of the many platform APIs available to those integrating with your application from outside of the Force.com platform, from environments such as Java, .NET, PHP, and Ruby. It also provided the best practices to ensure that your application and developers using these APIs have the best experience.
As stated in that chapter, these APIs are mostly focused on record data manipulation and querying, often known as CRUD. Leveraging the Salesforce APIs means developers wishing to learn how to integrate with your application objects can leverage the standard Salesforce API documentation and websites such as https://developer.salesforce.com/.
