What is the difference between ".NET Error Pages" and "Error Pages" in IIS7?

In IIS 7 (.5) on my Windows Server 2008 r2, there are two places for error pages: ".NET Error Pages" under "ASP.NET" in Features View, and "Error Pages" under "IIS" in the same view.

It seems like the first does not do anything, but the latter does (in my web application).

Why are there two, and what is the difference?

.NET Error Pages are for displaying custom error pages when ASP.NET encounters an error (e.g. 404 for an .aspx page, or exception thrown while rendering an aspx page)

The Error Pages are for displaying custom error pages when IIS encounters an error (before it hands off processing a request to ASP.NET). These would be shown when a regular .html page encounters an error.

There are two different areas in web.config for controlling the custom error pages.