Hi,
It seems nobody wants to take the shot to answer
Ok. Stored process is used for a lot of purposes. To keep it simple it's a sas code anyone can execute and receive the result of it without knowing anything about SAS. The easiest way is passing through the Stored Process web server to execute your SP.
In my case I use stored processes in Web Report Studio to aggregate seriously my data before reporting.
I also use it to create new SAS tables, the user just selects the metadata and sas code is created in a folder.
SP (stored processes) should be seen as a SAS program who can be executed without having any tool on your computer and simply by accessing the SP web service.
Hope I helped you.