Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
As the title says - I'm not sure i understand what they are!

Page outs are when your computer uses all of its RAM and it starts using the hard disk drive/SSD as RAM. Hard disk/SSD access is much slower than RAM, therefore your computer takes a performance hit.

If you have adequate RAM, you shouldn't see many page outs. It is a good indicator if you need more RAM.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.