Snow Leopard *private* folder? I am running 2 OS flavors on my 2010 Macpro, 10.6.8 Snow Leopard on one startup drive and the latest Yosemite on another. 

The Snow Leo drive contains a folder "private" that looked like it was 25GB but once opened and listing subfolders, dropped to under 2GB. What is the purpose of this folder? It doesn't seem to exist on the Yosemite drive at all. The drive is an SSD and anything I can do to keep it smaller would be great. This is the view of the whole drive -



The folder is named private but it's visible, and at the top level of the drive folder system.
All the files and folders within private are needed to run the Operating System and it exists in every version of OS X. The folder private has lost its hidden attribute.