This option is most often used for staff profile pages. Staff profiles are normally sitting under a listings page with a list of links to each individual profile. To have the staff page showing in left menu as well is not necessary and it also makes the left menu very long.
Click on the Searching & Navigation tab. Select the Exclude from left hand menu option. And while you are in the tab tick the Categories Web option as well. Click Save and Request publish and off it goes into the workflow.
