ol li {color:red}
<ol>
<li>First
<ul><li>Sublist item</li><li>Sublist item 2</li>
</ul></li>
<li>Second item</li>
</ol>
The inner list items are also descendants of ul so are coloured red
li {color:blue}
ul > li {color:red}
The inner list items are only descendants of ol so are coloured red