Two Groups of Categories for Posts

Well, that site is using the parent/child category way of things.
Their static heading “Categories” is using a parent category called “genre” and the links are all children of “genre”.

Under the heading “authors” they are using the parent category “authors” and children categories of authors using the author name.

Same thing with alphabetical.

If you’re wanting to make two groups of categories, I would do it like this.

Category A
Child 1
Child 2
Child 3
Category B
Child 1
Child 2
Child 3

Then in your sidebar, simply build the list to look the way you want linking to each subcategory.

Would you flesh this out just a bit for me? When I first attempted the parent/child categories, the Parent was showing up as a link in all the meta data of each post, as well as in the sidebar. How did filmforensics.com create a static category group name, ie. “Category,” “Author” and “Alphabetically” and how is the real Parent not showing up in the meta data for each post? How would I build the list to look the way I wanted? That area of my sidebar looks like this:

<h2>Navigation</h2>
<ul>
<li><a href="<?php echo get_settings('home'); ?>/">Home</a></li>
<li><?php wp_list_pages('title_li='); ?></li>
</ul>

<h2>Categories</h2>
<ul>
<?php list_cats(FALSE, ' ', 'name'); ?>
</ul>

Thanks for your help.

Update.
I started by changing the categories to be Parent/Child. And this time around, the Parent is NOT showing up in the meta data, OR in the sidebar, and all the categories are in alpha order in the sidebar, but not separated by the two Parents I created.

So I guess at this point, I just need to learn how to get the two Parents to separate in the sidebar. Thanks.