Multi-level list in Word 2010 refers to list that contains multiple levels having unique styles with proper indentation. By default, Word 2010 displays most commonly used multi-level lists, however, there is an option to create a new list or tweak the existing ones according to the requirements.
To customize or define multilevel list, under Home tab, from Paragraph group, under Muli-Level List gallery, select Define Multilevel List.
It will open up Define new Multilevel list dialog, here you can change Number format, format style, Position, etc. For modifying the levels of list, click the numbers at the top-left side of the window.
Once the new multi-level list is defined, click OK to view in list gallery.