Explain Public and Private pages?

All sets of pages are divided into two groups: Public Pages and Private Pages. 

Public Pages, by default, are accessible to anyone—including those who haven't logged in to the portal.

Private Pages, by default, are only accessible to the users who belong to the Organization or Community to which the pages belong. This means that an Organization's private pages would only be viewable by members of the Organization. The tabs for public and private pages have the same interface.