The file list2.wml provides all of the list rules in lists.wml (described in Section 11.4, "Lists") plus the following list rules:
L4BulletItem L4AutonumberItem L5BulletItem L5AutonumberItem L6BulletItem L6AutonumberItem L4NumberItem L4PlainItem L5NumberItem L5PlainItem L6NumberItem L6PlainItem
If you use list2.wml, you do not need to use lists.wml.