Processing a Work Item on the Internet 
Prerequisites
The workflow system has created a work item that represents the
Web form task. This work item is displayed in the Business Workplace of its recipients.Procedure
To process this work item as a Web form on the Internet:
You can then process the work item from your Web-Workplace.

Your Business Workplace on the Internet is only a "mirror" of your Business Workplace in the R/3 System. In other words, you could also execute the work item in the R/3 System.
In this case, it is not processed with a Web form but with the Web transaction that was generated from the task.