This is a brand new API method that was added in v188.8.131.52, and it lets you view a list of saved reports, generate a saved report asynchronously, and finally download that report in whichever format was selected (Acrobat, Word, Excel, HTML, or XML).
Here is the recommended order of using the API:
1. Saved Report API
2. Generated Report API
Note: You need to be connecting to the API as a System Administrator to use this API.