What is does
The Custom Menu Widget allows you Display any of the menus you have built in the Menu Manager right inside your sidebar. This is a great way to highlight important links in additional locations.
The settings for the Custom Menu Widget are very simple. You can add an optional title to your widget (or leave it blank) and then you need to select the menu you wish to display from the drop down menu. If you need to create a menu first, be sure to visit the Menu Manager at APPEARANCE > NAVIGATION MENUS