First, Oracle has a web site specifically for their Cloud applications: http://cloud.oracle.com.
Some of the information you can find there:
1. The Cloud FAQ page, at cloud.oracle.com/faq
2. Short videos on Cloud features.
Some informative examples:
(Note: Some were produced by Oracle and some by Oracle partners)
Oracle Cloud Application Foundation: Overview
Oracle HCM Cloud: Simplified UI for the Employee
Chart of Accounts Structure in Oracle Fusions Apps
Oracle Cloud Platform Services Overview
(Note: You will need an Oracle account to access this site)
Here's a description of OER: "Use the Oracle Enterprise Repository for technical information about integrating with other applications, including services, operations, composites, events, and integration tables. The classification scheme shows some example scenarios in which you can use the assets. The Oracle Enterprise Repository also includes diagrams, schematics, and links to other technical documentation."