Q:

what does this mean Inheritance Uses Computed Values

I'm reading this article
and in chapter "Inheritance Uses Computed Values" they say the following:

This is important for inherited values like font sizes that use
  lengths. A computed value is a value that is relative to some other
  value on the Web page.
If you set a font-size of 1em on your BODY element, your entire page
  will not be all only 1em in size. This is because elements like
  headings (H1-H6) and other elements (some browsers compute table
  properties differently) have a relative size in the Web browser. In
  the absence of other font size information, the Web browser will
  always make an H1 headline the largest text on the page, followed by
  H2 and so on. When you set your BODY element to a specific font size,
  then that is used as the "average" font size, and the headline
  elements are computed from that.

So if you have set text size in the browser to normal that 1em is about the same as 16px.
If you know choose to set a greater text size in browser the text will be greater.
So I wonder what are they trying to say with the article?

A:

It's basically saying it's all relative, so let's say your body is 16px, unless you specify specifically everything will be computed from this value for other tags.
if you use em, then 1em will be 16px for the top elements.
Example:
<div class="monkeyAss">Hello
<h1>monkeyAss2</h1></div>

.monkeyAss {font-size: 0.5em;}
.monkeyAss h1 {font-size: 1em}

Here your monkeyAss will be as expected 8px, for 1em, but then since h1 is inside another parent div, it's going to be also 8px, taking its value from its relative parent.  hope that helps.

