What does this option basically do? Does it free the unused memory? If so, how does it affect the performance? In what cases will I use it?
Excerpt from my copy of Windows Sysinternals Administrator's Reference 1st ed:
From personal experience, I just used taskmgr to view the memory changes.
Also, an image of the same below: - http://i.stack.imgur.com/V7AsR.gif
From the VMMap Help manual:
I would assume that the feature is similar for RAM map and that the "Empty Working Set" feature releases all physical memory.