VirtualPathutility Method definiton

Hi All,
Can Anyone plz tell me in detail what the below method does? I have searched on the web and dint find any satisfactory definition. I am trying to understand what actually happens and waht is the advantage of this method.
Please provide some light in the this.
<a href='<%# VirtualPathUtility.ToAbsolute("~/ProdcutsList.aspx?CategoryId=" + Eval("CategoryID")) %>'><%# Eval("CategoryName") %></a>


Thanks for your help,
Saleem
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