The fourth mentioned folders (RadControls, Scripts, TabControl and radSkins) are part of the classic version of RadControls for ASP.NET. This product is obsolete and not supported since 2009 in favor of Telerik UI for ASP.NET AJAX.
The RadControls and its inner folders contain the resources files of the classic controls. If you still use the classic controls you will need these folders to operate. If you use UI for ASP.NET AJAX, you don't need these folders since most of the resources are embedded in Telerik.Web.UI assembly.
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