List can be nested one inside the other. For creating a nested list use the second list as the item of the first(outer) list
snippet
<html>
<head></head>
<body>
    <ul type="square"> Header of unordered list
    <li>
        <ul> Header of unordered list
	    <li> Inner list 1st item
	    <li> Inner list 2nd item
	    <li> Inner list 3rd list item
	<ul>
    <li> 2nd list item
    <li> 3rd list item
    <ul>
<body>
<html>
Output
     Header of unordered list    -          Header of unordered list	    -  Inner list 1st item	    
-  Inner list 2nd item	    
-  Inner list 3rd list item	    -  2nd list item    
-  3rd list item    
 
 
  Note
The inner most list will be double indented.The inner most list items are rendered with different item