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