This is the place were you Add new Sidebars (widget areas) for your theme.
Simply type-in the name for the Sidebar you need in the Sidebar Name text box, and click Add.
Hit Save Options, then Refresh your page, and you’re done. Remove button removes unwanted sidebars.
To add widgets in your newly created Widget Area, navigate to Appearance >> Widgets and you’ll find your sidebar on the right area. Drag and Drop widgets from the left area or click on the selected widget and choose the sidebar you want.