Left Navigation (Drill-Down) Menu
The left navigation menu (for releases after June 2014) will automatically drill-down (filter) the user’s selection to display additional filtering (results limiting) selections.
You can turn on/off features that will be included in the left menu system in the CMS area under :
CMS > Left Drill-Down Menu
You can include the menu automatically on the site home page and CMS pages when editing an individual CMS managed page or when editing the site home page content.