lets say you have this HTML
<div id="top"><p class="text">blah blah blah</p></div><div id="btm"><p class="text">blah blah blah</p></div>
Lets pretend that the text in both the top and btm are the same font, size, etc except we want the top to be red and the bottom to be blue.Using nesting we can write a generic .text class that applies to both and then 2 specific classes that deal with the color...saves use repeating the common stylesCSS
.text{ font-family: sans-serif; font-size: 13px; font-weight: bold;}#top .text{ color: red;}#btm .text{ color: blue;}
Does that clear things up?