When a process requests a page that is not currently in its working set, the memory manager will look first in the physical memory of the system. This is called a soft page. If the memory page is not in physical memory, the page will have to be brought from disk. This is called a hard page. This gauge shows the percentage of soft pages versus hard pages.
On a system that has a low level of activity, Pages found in RAM will be at or near 100%.