ASP.NET MVC's Content/Themes/base Directory

What's the purpose of the Content/Themes/base directory in an ASP.NET MVC application? I see that it has some images (which as far as I can tell, are not used); and a bunch of jQuery CSS file开发者_Go百科s.

What are these files for? Are they used by default in a new ASP.NET MVC application?

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jQuery UI is included with new ASP.NET MVC projects; these files are used by all the different widgets. If you're not going to use jQuery UI, or if you want a custom download package (available from their website), you can delete all of these files (and the references to them in the layout/master page file).