Difference between Page Reads/Sec in "Memory" and "Buffer Manager" in perfmon

Hi

I'm capturing some performance stats of a sql server instance and Performance Objects "Memory" and "Buffer Manager"both have a counter for "Page Reads/Sec". I've read the definitions a few times and it's not sinking in what the difference is for the counter between the 2 performance objects and i can see the values returned by perfmon are somewhat different.

Could anyone explain what the difference is?

Cheers