If you are unfamiliar with Business Processes and Work Items, you should read the topics under Basic Business Process Concepts.
Since the BPM Add-in leverages the Microsoft Office 2007 ribbon, it cannot be used with previous versions.
If you don't know if the Oracle BPM Add-in is installed in your system, open one of the applications listed above, and look for the Business Processes tab in the ribbon. If it is not present, the BPM Add-in is not installed or not enabled.