There are multiple page templates available with different layouts.

Default Template
This page template has no left nav, but has a right sidebar for widgets

Full Width
This page template goes from left to right with no left nav or right sidebar.

Three ColumnĀ 
This template has the left navigation, main content in center and a right sidebar for Widgets and a gallerys

Two Column
Subnav on left, main content on right

How does the nav work on this page
The left navigation displays the parent/child pages of the current page. So here Page Templates is the parent, and each sub page is a child.