brendaegeland

A common web design pattern is to have a primary navigation with the top level pages, and then a separate 
navigation element on each page that shows only those pages related to a common top-most page. This widget helps 
to build those secondary navigation elements.
If your page structure was like this:
<ul>
<li>Home</li>
<li>About</li>
<li>— Our History</li>
<li>— Our Staff</li>
<li>— — Employment Opportunities</li>
<li>Services</li>
<li>— Widget Development</li>
<li>— Gadget Deployment</li>
<li>Contact Us</li>
</ul>
and you added the widget with its default settings to a sidebar, it would create a list like this:
<ul>
<li>About</li>
<li>Our History</li>
<li>Our Staff</li>
<li>— Employment Opportunities</li>
</ul>
on any of the pages in the About subtree. Notice that the top-most ancestor, About, is included as the first element of the list.
<h4>Options</h4>
<ol>
<li>Title. The widget title. If left blank, it defaults to the title of the top ancestor page.</li>
<li>Show Title. Maybe you don’t want a title. Just turn it off here.</li>
<li>Top Page. You can select one of your pages to be the top page, or you can choose Default, which determines the top-most ancestor of the page being displayed.</li>
<li>Menu Class. Gets applied to the outermost <ul> element.</li>
<li>Before Links. HTML to be inserted before links in the list.</li>
<li>After Links. HTML to be inserted after links in the list.</li>
</ol>

Subpages in Context

Lists pages and subpages for a given page, or the top ancestor of the current page and all of the ancestor's descendants

swedish boy

No configuration at all. Throw in the widget in your sidebar and it shows all subpages of page with wp_list_pages.

Children Pages

Displays children pages of the current top-parent page in a sidebar widget.

Subpages in Context vs Children Pages